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PSAS Avionics Node Front End for LV2b Rocket To

1. Equipment o Arbitrary function generator o Various resistors and potentiometers o Oscilloscope Experiment o For this experiment we will disconnect the Circuit Breaker Block from the Switcher We will disconnect the feedback from the 3 3 V SPS output to U251 input pin and directly attach a voltage source to the input pin which we can step to force U251 to turn Q251 on and off which will trigger an overcurrent event as seen by U250 Another experiment is to apply a resistor to the output of U251 namely the node between R252 and R253 and vary that resistance to cause a direct overcurrent event 7 1 2 2 Quiescent current draw of U250 e Objectives o With the whole SPS in a shutdown or standby mode U250 is draws the most quiescent current being between 1 mA and 2 mA We want to observe the transient response of the Front end Passive Block as the voltage is applied to its input and possibly having its own transients Equipment o Arbitrary function generator o Various resistors and potentiometers o Oscilloscope Experiment o We will disconnect the Front end Passive Block from the rest of the SPS and apply a DC load at its output and apply a ramping voltage source at the input simulating the power bus We will step the voltage in varying times and magnitudes 7 1 3 Switcher 7 1 3 1 Minimum discontinuous mode current e Objectives o Besides inductor saturation and thermal dissipation we want to avoid U200 from entering d
2. Part Description e 180 V 0 6 A SOT 23 Cut Tape ROHS Compliant Micro Commercial Co MMBD1501 TP Digi Key p n MMBD1501TPMSCT ND 2 00 10 http 59 120 39 77 mccsemi up_pdf MMBD1501 A 1505 A SOT 23 pdf Purpose e This diode is used to charge the boost cap C202 Specifications Calculations e It should have a voltage rating gt gt 20 V and a current rating of several hundred mA Since this is a high power diode in the SPS we wanted the package to be bigger than the MiniPower 2P but not to big so we chose an SOT 23 5 1 4 8 Buck Catch Schottky Diode CR200 Part Description e 30V 1 5A 4ns New MiniPower 2P Cut Tape ROHS Compliant Panasonic SSG MA2Q70500L Digi Key p n MA2Q70500LCT ND 0 83 1 http www semicon panasonic co jp ds eng SKH00017BED pdf Purpose e This is the buck catch output diode Specifications Calculations e Using the formula on page 9 in the LT1767 datasheet we calculated the average DC current that CR200 should be able to handle Ipavg lO Vin Vout Vin where lo is the output current of the SPS Vin is the voltage at the input pin 2 of U200 and Vout is the SPS output voltage With Vout 3 3 V and using the worst case lo 1 A and Vin 20 V values Id avg 835 mA Even though the maximum specified lo 400 mA and F200 is rated at 500 mA we used lo 1 A because the fuse had a finite opening time of about 1 s upon which L200a b could draw higher currents through CR200 not
3. 64 MAC etc Development Tools Must have current and active OSS tools gcc gdb binutils etc Must have useful open debugger protocol e g JTAG Packaging Must have usable packaging packaging that can be used on two layer boards o Must be a Quad Flat Pack or QFP e g a TQFP or LQFP or possibly a BGA with lt 32 pins o QFP should have lt 64 pins gt 100 pins is possible but a pain 144 pins absolute maximum Peripherals Must have on board memory gt 128 KB flash gt 32 KB SRAM Must have necessary communication buses CAN and or USB Should have one or more serial buses UART SPI etc Should have a gt 10 bit ADC Should have gt 3 PWMs Should have a watchdog timer Should have brown out reset Computational Horsepower Must have gt 10 MIPS but should have gt 60 MIPS Power Consumption Should have reasonable voltage requirements e g 3 3V only best or 3 3V 5V Should have low power modes Cost Should be relatively low cost in small quantities 3 2 2 32 bit Microcontrollers considered There were two microcontroller architectures considered initially ARM Advanced RISC Machine and PPC Power PC ARMs are popular microcontrollers with good open source support On the other hand PSAS has a grant from IBM to use Power PC microcontrollers on the rocket A quick look at PPC manufactures revealed the microcontrollers did not meet our package size requirements the smallest p
4. With a standard operating system there is no guarantee that time constraints of a program will be met This is disastrous in an avionics system when a delay in sensor data or recovery node commands may mean the parachute is not deployed in the 5 second apogee window RTOS Requirements e Hard real time performance e Fully open source e Small footprint e Ported to several ARM processors e Integrated debugging tools GDB There were two RTOS that fit all requirements eCos http ecos sourceware org and FreeRTOS http www freertos org PSAS members have more experience with eCos so eCos was chosen 3 3 1 eCos eCos stands for embedded Configurable operating system eCos is configurable because you can choose which features you want to compile into your embedded operating system This allows you to tweak your options if you don t have a lot of memory in your embedded system For example a programmer can choose to compile GDB stubs into their program and eCos This is great for debugging but can inflate the code size After the person is done coding and wants to run the program out in the field they can recompile eCos without GDB stubs to save memory 3 4 System Block Diagram Here is the new avionics system design LV2 Rev B Avionics System Umbilical Cord 19V shore power Launch relay iteriock Inertial Measurement Unit Avionics Power System 16 8V 4Ah Battery Pack Flight Computer od some oe eA 1A L
5. Action Group debug signals The port also provides access to the UART used for programming the on chip flash memory There is also 3 3 volt power and digital ground provided on this port should a special debug feature need it Power Good and Shutdown e These signals between the microcontroller and SPS will 1 allow the microcontroller to detect a good bad power condition so it could do some possible corrective or evasive action and 2 allow the microcontroller to shut down the node power in case of emergency or the need for a power up reset The hot swap controller circuit breaker block will reset and restart the SPS after a specific period of time provided the external power is still acceptable Breakout of signals to application specific area e This is where the future application specific portion of the node accesses the resources provided by this front end module Status LEDs e These are simple Red and Green LED s driven by microcontroller general purpose IO The intent is to provide a future user defined status indicator for what ever reason Test points e There are test points identified on the schematic and board intended for validation of specific functions such as SPS Sync Clock Power Good SPS Shutdown These typically would be used during initial testing but my be of use later when the application specific functions are being tested and debugged Configuration trace cuts or solder jumpers e There are jumpers that can b
6. C type 0805 0805 0805 SOT 23 SOT 23 SOT 23 0805 10 pack 10 pack ay Datash eet 10 pack 10 pack 10 pack 10 pack each each each 10 pack 6 Software 6 1 Introduction To paralellize the software and hardware development software for the LPC2148 was developed on an evaluation board from Olimex The developed software will work exactly the same on the node front end since it only relies on the type of ARM chip Two software programs were developed and shown to work on the Olimex evaluation board e asimple program to turn on and off an LED e aneCos port to the LPC2148 The eCos port was an optional requirement for our project and puts software development ahead of schedule 6 2 Tools used Our industry sponsors required all software used in this project to run under Linux Running under Windows was optional but software that is open source is a big win If the software is open source we can modify it when we find bugs and give the source back to the community 6 2 1 Serial Terminal The LPC2148 chip can communicate over the serial port It will respond to special In System Programming ISP commands specified in the Philips datasheet These commands include but are not limited to setting the baud rate writing to RAM copying from RAM to flash reading from memory and echoing the part ID or boot code version The LPC2148 serial communication can easily be tested using a terminal tha
7. V Tant T491 Series 7343 31 EIA Cut Tape ROHS Compliant Kemet T491D226K025AT Digi Key p n 399 3782 1 ND 0 65 1 htto www kemet com kemet web homepage kechome nsf vapubfiles F3102T491 pdf file F3102T491 pdf Purpose e C203 acts as a noise filter between the power bus and SPS It also serves as a local energy storage node Specifications Calculations e It needs to have a voltage rating greater than 20 V and a low equivalent series resistance ESR thus a tantalum capacitor was chosen due to their low ESR at a higher capacitance 5 1 1 4 2 C204 Part Description e 0 33 uF 50 V 0805 X7R Cut Tape ROHS Compliant Murata Electronics North America GRM219R71H334KA88D Digi Key p n 490 3327 1 ND 3 09 10 http search murata co jp Ceramy image img PDF ENG GRM219R71H334KA88 pdf Purpose e C204 is a high frequency noise filter between the power bus and SPS It did not have to have as high a capacitance as C203 so the trade off was to get a lower value at a low ESR Specifications Calculations e It needs to have a voltage rating greater than 20 V and the capacitance value was not very critical but should be much lower than C203 5 1 1 5 Power Bus Input Voltage Suppressor TVS200 Part Description e 18 V SMB Unidirectional Cut Tape ROHS Non Compliant Diodes Inc SMBJ18A 13 Digi Key p n SMBJ18ADICT ND 0 89 1 http www diodes com datasheets ds19002 pdf Purpose e A transient voltage supp
8. bus the next generation rocket should use Numerous suggestions were thrown out from FireWire to MIL STD 1553 but only two communication buses were considered in depth the Universal Serial Bus USB and the Controller Area Network CAN bus 3 1 1 Bus Requirements 3 1 1 1 Avionics Team Requirements 3 1 1 1 1 Reliability The bus must be capable of handling EMI along with short and open conditions on the PHY layer The bus must tolerate the acceleration and vibration associated with a launch The bus should also have been used in real time systems where a failure in the bus might result in lives being lost such as medical equipment or automobiles The bus must provide a way for the software to prioritize messages so that system critical messages will be sent even at the expense of non critical messages 3 1 1 1 2 Performance The bandwidth of the bus must be large enough to keep data flowing and nodes operational Some nodes will require access to the bus on regular intervals while others will be sending non periodic data packets The previous rocket s CAN bus provided 1Mbps and at most 40 of that bandwidth was used The bandwidth requirement may change so more bandwidth would be better 3 1 1 2 Software Team Requirements 3 1 1 2 1 High level software control The Software team would like the high level software to deal with retransmission of corrupted packets and packets that were not received by the intended recipient Syste
9. cd4020b pdf Purpose e Divide the 12 MHz clock by 8 to generate a 1 5 MHz SPS sync clock Specifications Calculations e 8 2 so pick off signal at Q3 This divider is also useful for other application specific functions to be identified later since it is simultaneously creating all versions of the system clock divided by 2 through 2 inclusively For convenience have placed below a diagram which shows the internal configuration of this divider Terminal mo HA 10 Vo Terminal no 7 ta Vigg Image from TI CD4024 datasheet Fig Glue 8 5 2 6 RTC crystal oscillator e Chapter 19 in the Philips LPC2148 user manual describes operation of the internal Real Time Clock The clock keeps time and date in user acessable registers described on page 276 of the user manual The power for the clock is brought out externally on pin 49 and is seperate from the main power so a battery could power the clock when the CPU is powered off This will allow the clock time to remain current It is intended this power be provided by an external 3 2 volt lithium coin cell and so pins have been brought out to the user specified area for this It is also possible to connect the clock power to the main 3 3 volt supply rail if a battery is not available 5 2 6 1 Oscillator load capacitors C283 C284 5 2 6 1 1 C283 5 2 6 1 2 C284 Part Description e 22 pF 50V Ceramic chip NPO 0805 Panasonic ECJ 2VC1H220J Digikey P N PCC220CNCT ND http ww
10. device can be exposed to during board level solder attach and rework This limit permits only the use of solder profiles recommended in the industry standard specification JEDEC 020A paragraph 7 6 Table 3 for IR VPR and convection reflow Preheating is required Hand or wave soldering is not allowed which may or may not present a problem The invoice we received for the ordered samples specified that they were MAX5902AAETT in a SOT23 package they were in the SOT23 package The datasheet however specifies that the MAX5902AAETT is a TDFN part which does not have a special solder specification and all SOT23 part numbers have the symbol suffix The symbol suffix in the invoice means its a lead free part There are some discrepencies 5 1 2 3 MAX5902 External P MOSFET Q250 Part Description e 60 V 3 A SOT 23 6 P Channel MOSFET Cut Tape ROHS Compliant Zetex Inc ZXMP6A17E6TA Digi Key p n ZXMP6A17E6CT ND 1 04 1 http www zetex com 3 0 pdf ZXMP6A1 7E6 pdf Purpose e This is the external PMOSFET of U250 which will turn off given that there is one or more of the four trigger events as described earlier See U250 U250 uses the RDS on of the saturated Q250 as a current sense resistor which generates a Vds voltage which is detected across the Vs Pin 1 and DRAIN Pin 2 pins and if it is greater than some threshold voltage U250 will switch Q250 off thus breaking the circuit Specifications Calculations e The maximu
11. enabled the 2148 can generate a brown out interrupt when Vpp goes below 2 9 volts Additionally the 2148 will internally assert reset if Vpp goes below 2 6 volts We want to choose the MCP130 threshold voltage to allow this brown out interrupt to occur and could override the low Vpp reset assertion having this provided by the MCP130 instead Another constraint to choosing the MCP130 threshold voltage is to allow normal SPS load regulation to offur and not cause an unwanted reset Jacob assures in the SPS design that Vpp should never go below 3 0 volts under normal output ripple conditions Infact he indicates that is Vpp does go below 3 0 volts this is a fault condition and something is wrong and a reset would be appropriate Figure Glue 5 shows the allowed duration of a voltage drop out transient allowed before a reset is generated by the MCP130 Normal operation of the SPS is around Vrrip Voo 0 3 volts which allows a drop out transient of about 3 us This is well within the SPS spec according to Jacob A final constraint is the length of time reset is asserted after power up Figure Glue 6 illustrates this relationship with tapy being approximately 275 ms for the MCP130 variant chosen The LPC User Manual section 3 10 indicates this needs to be at least 10 ms for the first reset as power is first applied and can be as little as 300 ns for subsequent resets after to chips oscillator is up and running tr VTRIP win Vo D Tr
12. high turning Q251 on When this happens it pulls pin 2 of U250 very close to ground and current flows through R253 and Q251 Now that pin 2 is close to ground and pin 1 is normally close to the power bus voltage this is much greater than 300 mV this causing an overcurrent trigger event for U250 R253 limits the extra current pulled through Q251 when it is turned on Specifications Calculations e In normal SPS operation the voltage drop across Rcb will be less than 300 mV and R253 is connected to the high impedance pin 2 of U250 so no current flows through it If there is an overvoltage trigger event at the SPS output Q251 is turned on conducting current through R253 which will have a voltage drop of approximately 300 mV less than the power bus voltage Vazs3 16 8 V 300 mV 16 5 V This results in a current boost of about IRo53 16 5 V 47 kohm 351 uA which is negligible 5 1 3 3 TLV3012AIDBVT External Logic Level N MOSFET Q251 Part Description e 100 V 170 mA RDS on 10 ohm Vgs 4 5V SOT 23 Cut Tape ROHS Compliant N Channel Logic Level MOSFET Infineon Technologies BSS123E6327 Digi Key p n BSS123INCT ND 0 36 1 http rocky digikey com WebLib Infineon Web 20Data BSS123 pdf Purpose e This is a logic level NUOSFET When an overvoltage at the 3 3 V SPS output occurs U251 will output a logic high turning Q251 on and thus conducting current through R253 The current flowing through R253 also flows through R
13. microseconds V dt can be found using the following calculations V dt vin Vout T D where T is the period of the switching frequency 1 f and D is the duty cycle of U200 Using the formula on pages 1 and 2 in the National Semiconductor Application Note An 1197 D Vout Vd Vin Vd Vsw Therefore D 3 3 V 0 37 V 20 V 0 37 V 66 mV 18 1 T 1 f 1 1 5 MHZ 667 ns The applied volts microseconds therefore equals to V dt 20 V 3 3 V 667 ns 0 181 2 01 V us Given L200a 47 uH we can solve for di delta_I V dt L200a 42 82 mA Since the applied volts us we calculated is across the whole 100 uH 47 uH 2 94 uH inductance we need to cut this value in half since the all the parameters taken from the SD3118 470 R datasheet is for a single 47 uH inductor Therefore the di we will be using for further calculations is delta_l di di 2 21 4 mA We need to solve for Bp p to find the core losses from the graph on page 3 in the SD3118 470 R datasheet Bp p K L200a di 12 47 H 21 4 mA 12 1 mT The graph on page 3 of the SD3118 470 R datasheet does not include a switching frequency of 1 5 MHz but estimating from the spacing between the different frequencies we extrapolated the core losses to be equal to about 11 mW The DC power losses is simply the direct current resistance DCR times the average DC current which is Pde Idc POR 600 mA2 1 21 ohm 109 mW The DC po
14. on again Under normal operating conditions no UVLO event and assuming that there are no long or catastrophic transients U251 should always be on This design will always keep U250 on which will minimize any unknown states at the comparator output resulting from U251 turning off then on again etc Upon initial power up we assume that the output of U251 will be logic low keeping Q251 off to prevent a false overcurrent event for U250 which may prevent the SPS from working as U250 will never turn Q250 on and will just cycle This seems unlikely because upon initial power up U251 has no power and cannot output logic high However as the 3 3 V SPS output is being brought up the output of the comparator is undefined which is not good being directly connected to the gate of Q251 but we still think that Q251 will remain off or will rapidly switch off if it is ever on after the transients Specifications Calculations We calculated the needed amount of charge Qt C250 would have to store such that U251 would have power for at least 0 5 s our specified amount of time U251 should have power during these events given that the SPS output voltage dropped by 1 V from which we calculated C250 s capacitance C250 Qt 1 2 Iq tp Vp where Qt Input Capacitance Vt Reverse Transfer Capacitance Vin Iq 2 8 uA ts 0 5 s Vp 1V Qt is the sum of products of the input capacitance of Q251 times the maximum threshold voltage plus
15. the reverse transfer capacitance of Q251 times the maximum Vds swing namely Vin Iq is the supply current of U251 tp is the amount of time we want U251 to have power Vp is the amount of voltage the SPS output drops and the 1 2 term is a fudge factor because Qt is dependent on some other factors not explicitly shown tp was specified to be 0 5 s this time is the time C250 can supply power to U251 which is longer than the propagation delays mentioned above including some margin just in case any trigger events do not go away and U250 has to go through another 150 ms start sequence If the trigger events remain longer than the 0 5 s then U251 turns off and the whole SPS will go through another initial power up sequence Vp 1 V i e the input voltage V pin 6 to U251 can drop to about 3 0 V 1V 2V Iq 2 8 UA see page 3 in the TLV3012 datasheet Qt 85 pF 2 V 15 pF 20V 470 pC see page 3 in the BSS123 datasheet C250 1 40056 uF we decided to chose a 2 7 uF cap to give us a little more tp due to any unknown delays and the like we did not consider 5 1 3 7 TLV3012AIDBVT Overvoltage Detection Cap C251 Part Description e 0 015 uF 100 V 0805 X7R Cut Tape ROHS Compliant AVX Corporation 08051C153KAT2A Digi Key p n 478 1359 1 ND 2 64 10 http rocky digikey com WebLib AVX Web 20Data X7R 20 C pdf Purpose e 251 is used as a low pass filter to node IN pin 3 of U251 and as positive feedback to make the comparato
16. tor deel ORO SCS TOS select the fast version of the I O ports FIOODIR O200000400 7 pin POL10 is an Output everything else is input after reset FIOOSET 0x00000400 led off FIOOCLR 0x00000400 led on endless loop to toggle the red LED P0 10 while 1 for j 0 43 lt 5000000 j wait 500 msec FIOOSET 0x00000400 red led off for j 0 3 lt 5000000 j wait 500 msec FIOOCLR 0x00000400 red led on The snippet from main c is fairly simple It makes the GPIO pin P0 10 an output and then turns the LED on and off by setting and clearing the GPIO output The remaining 100 lines of main c contains interrupt routine stubs and a function to initialize the chip The initialization function sets the main clock frequency to 60MHz an unacceptable rate to use USB with initializes the current controlled oscillator sets the number of clock cycles to fetch memory out of flash enables MAM and sets the peripheral clock to the main clock frequency This code along with the start up assembly code and memory map file would not be necessary if the program was running under eCos 6 4 5 Compiling and Downloading Instructions Once the necessary changes are made to the makefile you can simply type make in the demo directory This will compile the program into a main out and a main hex file Now you ll need to use lpc21isp to download the main hex file to the LPC2148 Set switch 1 on the Olim
17. up a control endpoint that would send an I m alive packet every USB frame The host side would look at the frame number and endpoint number included in the USB frame to make sure that no packet was dropped This test could be done without an eCos USB driver This simple test might be used in flight to indicate that a node is functional Since isochronous and interrupt transfers can only take up 90 of the USB frame the test would not take away bandwidth from sensor data and would provide valuable feedback 7 3 3 USB Performance Testing e Objectives o Test USB performance Software Needed o eCos USB driver eCos isochronous USB support Plan o When the PSAS software team suggested switching from CAN to USB avionics team members were initially concerned about USB packet loss and bus speeds There are no published papers on USB bandwidth tests just the specification s assurance that it should just work Another concern is that the USB peripheral on the ARM microcontroller might be inferior The USB software test should push USB to its packet size and bandwidth limits We are especially interested in tests on isochronous transfers Isochronous transfers are not retransmitted so we want to make sure that the packets get through uncorrupted A good test would be to create a configuration where the sum of the isochronous endpoint max packet sizes will use up the entire USB frame The USB specification states that each received packet will con
18. 0 mA 50 V 1206 Fast Acting Short Time Lag ROHS Compliant Wickmann USA Inc FCD120500TP Digi Key p n WK6213CT ND 0 56 1 http rocky digikey com WebLib WICKMANN Web 20Data FCD1 2 pdf Purpose e This fuse protects the SPS from currents greater than 500 mA Its direct purpose however is to protect the power bus from a short circuit fault on the SPS side Specifications Calculations e Since the specified maximum SPS current is 400 mA we chose a fuse rated at 500 mA The opening time for the fuse according to its datasheet is 1 s at a current of about 1 15 A Currents below 1 A are several hundred seconds therefore this fuse will only protect the SPS or power bus from gross currents due to some fault on either side power bus or SPS and not to keep the SPS output current within spec that is U250 s job 5 1 1 3 DC Path From SPS Node GND to Chassis GND Resistor R215 Part Description e 100 kohm 0805 1 1 8 W Cut Tape ROHS Compliant Rohm MCR10EZHF 1003 Digi Key p n RHM100KCCT ND 0 38 10 http www rohm com products databook r pdf mcr10 pdf Purpose e R215 provides a DC path from the SPS ground to chassis ground See page 29 of the CAN Node Switch Mode Power Supply SPS 200 section in the Component Design for LV2 Power Electronics Except Main Battery engineering design notes Specifications Calculations e 100 kohm worked 5 1 1 4 Power Bus Input Caps C203 C204 5 1 1 4 1 C203 Part Description e 22 uF 25
19. 0V switching supply with battery backup MOSFET switches Cylindrical Patch Antennas 3 4 1 Block Diagram of Node The scope of this project is within the dashed line LV2b Avionics Node Switching power supply Application specific i circuits e g IMU GPS 32 bit microcontroller Node Front End Power bus Comm bus Each generic node front end contains a switching power supply SPS some glue circuitry and an ARM microcontroller running a real time operating system RTOS 3 4 2 Switching Power Supply SPS Block Diagram Front end Power Bus Passive Block 4 3 3 V SPS Switching Power Supply SPS Block Diagram Power Bus e This is the 16 8 V four 4 2 V Li lon cell batteries power bus where all LV2b nodes derives their power from Front end Passive Block e This block acts as a high frequency electromagnetic interference EMI filter using an input choke and bypass capacitors Also there are two protection features in this block 1 fuse and 2 input overvoltage protection There is a DC path between the SPS ground and the rocket s chassis Circuit Breaker Block e This block protects the SPS from overcurrent events The maximum specified output current is 400 mA If there is an overcurrent draw below the rated fuse current 500 mA or if the fuse fails to blow or opens in a longer amount of time this block will disconnect the rest of the SPS from the power bus The onl
20. 42 V for an overvoltage trigger event at the SPS output It is powered by a secondary supply consisting of CR250 and C250 Also it has a pseudo low pass filter consisting of C251 and its output pin 1 with the input being pin IN pin 3 See CR250 C250 and C251 respectively Specifications Calculations e We wanted a low power push pull output comparator to get rail to rail output swing approximately 200 mV to 3 1 V and have reasonable switching and rise fall times on the order of several microseconds and nanoseconds respectively We tied the IN pin pin 4 to the internal reference voltage REF pin pin 5 which will be compared to the divided SPS output voltage at its IN pin pin 3 See R254 R255 and C251 The undervoltage protection is actually provided by CR250 and C250 where U251 will remain powered for a specified amount of time if the 3 3 V SPS output rail drops See CR250 and C250 5 1 3 2 TLV3012AIDBVT Overvoltage Detection External N MOSFET Current Limiting Resistor R253 Part Description e 47 0 kohm 0805 1 1 8 W Cut Tape ROHS Compliant Rohm MCR10EZHF4702 Digi Key p n RHM47 0KCCT ND 0 38 10 http www rohm com products databook r pdf mer10 pdf Purpose e R253 along with Q251 will emulate an overcurrent trigger event as seen by U250 when an overvoltage at the SPS output trigger event as seen by U251 occurs See Q251 When the SPS 3 3 V output rises above a certain threshold the output of U251 goes
21. CD4024 provides SPS Sync o t8 MCP130 releases CPU reset o t9 First instruction executed o t10 PLL registers programmed and 48 MHz USB clock available Key timing issues Interval Description t4 t5 Determined by LPC2148 16 48 Determined by MCP 130 7 and is called Trpu 13 17 The SPS oscillator is free running 7 2 5 ARM Glue final block testing e Verify consistent start up e Verify crystal response to vibration 7 3 Software Details When Vdd goes below 2 9 V the LPC2148 issues a brown out interrupt When Vdd is below 2 6 V the LPC2148 internally asserts it s reset See page 42 Typical time is 275 ms See MCP130 Fig 2 3 The LPC2148 requires 10 ms see page 38 of users manual SPS_Sync has not yet been provided The SPS should be running around 1 25 MHz 7 3 1 Node Testing e Objectives o Test firmware Software Needed o serial port test o Blinky Demo o eCos Port o Once the generic node front end has been fabbed and the Glue and SPS logic tested the next step is to bring up the firmware on the board The process will be similar to bringing up the Olimex evaluation board verify communication through the serial port download a simple program to blink an LED and then download the same program running under eCos 7 3 2 Initial USB Testing e Objectives o Demonstrate simple USB communications Software Needed o simple USB software Plan o A good first test of the USB software would be to set
22. CM201 Part Description e 16 pin right angle connector JST 16PS JED Available from JST htto www jst co uk Purpose e Provide interconnection between the JTAG and UART ports to the outside world The UART access allows in circuit programming of the flash memory Chapter 21 of the LPC2148 User Manual describes programming Also see section 6 2 2 ISP Software of this report Specifications Calculations e Small small small Right angle Something we trust regarding pin integrity 2006 07 05 TAB and ADG are now thinking 0 5mm pitch LCD style board to board connector Typical Hirose DF17A 4 0 40DP 0 5V 57 from Digikey Using the high density LCD connector we double up the pins by going straight through the part connecting one side to the other with 0 5 mm parts we take every other one on the other side of the connector and via it to the bottom so from a 30 pin part we get 15 connections 8 on top and 7 on the bottom from the far side via vias 5 2 7 2 Pull up down resistors R283 284 285 286 287 288 Part Description e 10 0 K ohm resistor Chip 1 Thick film 1 8 watt Package 0805 Panasonic ERJ 6ENF1002V Digikey P N P10 0KCCT ND http www panasonic com industrial components pdf AOAQ000CE2 pdf Purpose e Pull up down resistors on JTAG port pind Not sure yet of the purpose suspect to assert a default signal when the port is not connected to a JTAG ICE This was directly copied from the Olimex Evaluation oard
23. D RHM649CCT ND RHM100KCCT ND RHM61 9KCCT ND P 82DCT ND RHM47 0KCCT ND RHM18 2KCCT ND PSAS SPS PSAS SPS PSAS SPS PSAS SPS PSAS SPS PSAS SPS PSAS SPS PSAS SPS PSAS SPS PSAS SPS PSAS SPS PSAS SPS PSAS SPS PSAS SPS PSAS SPS 5 1 7 2 Coiltronics BOM Qty Coiltronics SKU Cust ID 5 5 SD3118 470 R CMS1 11 R Part PSAS SPS L201 L202 D201 F200 Q250 Q251 TVS200 R200 R210 R25 1 R255 R201 R206 R209 R214 R215 R250 R252 R253 R254 Mfer PSAS SPS L200a L200b Coiltronics 47 uH Inductor Coiltronics CML Innovative Technologies Inc Wickman USA Inc Littlefuse Inc Zetex Inc Infineon Technologies Diodes Inc Rohm Rohm Rohm Rohm Rohm Rohm Panasonic ECG Rohm Rohm Description Mfg Num 1 9V Orange LED 500 mA Fast Acting Fuse P Channel MOSFET N Channel Logic Level MOSFET Unidirectional Voltage Suppressor 10 kohm Resistor 17 4 kohm Resistor 60 4 kohm Resistor 649 ohm Resistor 100 kohm Resistor 61 9 kohm Resistor 0 82 ohm Resistor 47 0 kohm Resistor 18 2 kohm Resistor Price Stock Package SD3118 470 R 100 uH Inductor CMS1 11 R Torodial SMT CMDASBA7D1S FCD120500TP ZXMP6A17E6TA BSS123E6327 SMBJ18A 13 MCRI10EZHF1002 MCRI10EZHF1742 MCR10EZHF6042 MCR10EZHF6490 MCR10EZHF1003 MCR10EZHF6192 ERJ 6
24. FB resistor network which sets the value of Vout of U200 Specifications Calculations e Using the formula on page 7 in the LT1767 datasheet R201 R200 Vout 1 2 V 1 2 V R200 0 25 uA where R200 10 0 kohm and Vout 3 3 V R201 equated to 17 54 kohm the closet standard value was 17 4 kohm 5 1 4 12 LT1767 FB Resistor Network Shunt Caps C208 C209 5 1 4 12 1 C208 Part Description e TBD Purpose e Part of the frequency compensation of U200 Specifications Calculations e See pages 24 25 of the CAN Node Switch Mode Power Supply SPS 200 in the Component Design for LV2 Power Electronics Except Main Battery engineering design notes Also see pages 48 50 of the Linear Technology application note an 19 and see application note an 76 The value is TBD 5 1 4 12 2 C209 Part Description e 10 pF 50 V 0805 NPO Cut Tape ROHS Compliant BC Components VJO805A100JXACW1BC Digi Key p n BC1256CT ND 0 52 10 http www cooperet com library products PM 4313 20CMS Series pdf Purpose e Part of the frequency compensation of U200 Specifications Calculations e We used the same value as from the LV2 design See pages 24 25 of the CAN Node Switch Mode Power Supply SPS 200 in the Component Design for LV2 Power Electronics Except Main Battery engineering design notes Also see pages 48 50 of the Linear Technology application note an 19 and see application note an 76 5 1 4 13 SPS Output Power
25. JED JST 16PS JED CS10 CM415 32 768KDZFTR Price 11 88 0 50 0 84 0 48 1 65 2 10 0 49 0 49 0 69 Ste Package k 86 64 LQFP 14 an TSSOP SOT 23 6 100 SOT 23 3 CS10 1122 CM415 0805 0805 0805 Order Size each each each each each each each each 10 pack 10 pack 10 pack Data Sheet Datash eet Fi Datash eet ay Datash eet ay Datash eet Tr Datash eet LE Datash eet 30 10 10 10 30 10 5 wS 5 PCC103BNCT ND PCC180CNCT ND P9832CT ND P33 2CCT ND P10 0KCCT ND P604CCT ND BSS123NCT ND L71516CT ND L71508CT ND P1 50KCCT ND PSAS GLUE PSAS GLUE PSAS GLUE PSAS GLUE PSAS GLUE PSAS GLUE PSAS GLUE PSAS GLUE PSAS GLUE PSAS GLUE Note 1 C285 286 287 288 2 91 292 C289 290 L281 282 R281 282 R283 284 285 286 2 87 288 R289 290 Q282 D281 D282 R291 Panasonic Panasonic Panasonic Panasonic Panasonic Panasonic Fairchild Panasonic Chip X7R 10 nF Chip NPO 18 pF Chip EMI Filter Type EXCCET Chip 1 Thick film Chip 1 Thick film Chip 1 Thick film 0 54 0 60 EXC CET103U 0 685 Logic level N channel BSS123 0 36 LED Red LED Green Chip 1 Thick film NOTES 1 C285 286 287 288 291 292 should be a 100 nF cap not 10 nF Needs to be ordered 0805 0805
26. ND a C202 Pansonic ECG 5 399 3782 1 ND o C203 Kemet 5 490 3327 1 ND C204 ee North 5 l C205 5 a C206 5 ia C208 5 BC1256CT ND C209 BC Components 5 BC1298CT ND o C210 BC Components 5 399 3127 1 ND PSAS 250 Kemet SPS 5 478 1359 1 ND eg C251 AVX Corp 5 C252 C252a 15 MA2Q70500LCT ND o r 0 Panasonic SSG 5 MMBDISOLTPMSCT PSAS CR201 Micro Commercial Co ND SPS Description Switching Step Down Voltage Buck Regulator 22 uF Ceramic Cap 10 uF Ceramic Cap 0 1 uF Ceramic Cap 22 uF Tantalum Cap 0 33 uF Ceramic Cap 10 pF Ceramic Cap 0 1 uF Ceramic Cap 2 7 uF Ceramic Cap 0 015 uF Ceramic Cap 30V Schottky Diode 180V Rectifier Diode Mfg Num LT1767EMS8 ECJ 2FB0J226M ECJ 3YB1E106K ECJ 2YB1H104K T491D226K025AT GRM219R71H334KA88D VJO805A100JXACW1BC VJO805Y 104KXATWI1BC C0805C275K8PACTU 08051C153KAT2A MA2Q70500L MMBD1501 TP Price Stock 6 00 8 31 5 45 1 61 0 65 3 09 0 52 0 72 7 02 2 64 6 24 2 00 2716 4740 7640 21520 863 3090 80 60 3860 5300 4192 3000 Package 8 MSOP 0805 1206 0805 7434 31 0805 0805 0805 0805 0805 MiniPo wer 2P SOT 23 Order Size 1 10 10 10 10 10 10 10 10 10 20 L71515CT ND WK6213CT ND ZXMP6A17E6CT ND BSS123INCT ND SMBJ18ADICT ND RHM10 0KCCT ND RHM17 4KCCT ND RHM60 4KCCT N
27. On LED Current Limiter Resistor R214 Part Description e 649 ohm 0805 1 1 8 W Cut Tape ROHS Compliant Rohm MCR10EZHF6490 Digi Key p n RHM649CCT ND 0 38 10 http www rohm com products databook r pdf mcr10 pdf Purpose e R214 is the SPS Output Power On LED current limiting resistor Specifications Calculations e From the datasheet Vf 1 9 V resulting in a current limiting resistor of about R214 3 3 V 1 9 V 2 mA 650 ohms The closest standard value was 649 ohms 5 1 5 Secondary Voltage Supply 5 1 5 1 SPS Secondary Buck Catch Schottky Diode CR251 Part Description e 30V 1 5A 4ns New MiniPower 2P Cut Tape ROHS Compliant Panasonic SSG MA2Q70500L Digi Key p n MA2Q70500LCT ND 0 83 1 hitp www semicon panasonic co jp ds eng SKH00017BED pdf Purpose e CR251 along with C252 and L200a form the second buck switching voltage power regulator which will be eventually regulated down to 5 V possibly with a low dropout LDO linear voltage regulator For consistency we used the same Schottky diode as CR200 Also the general understanding was that this secondary buck will power specific parts like 5 V ADCs on certain nodes like the IMU and we expect that this diode s rated specs are more than enough Specifications Calculations e Using the formula on page 9 in the LT 1767 datasheet we calculated the average DC current that CR251 should be able to handle Id avg lo Vin Vout Vin where
28. Portland State Aerospace Society PSAS Avionics Node Front End for LV2b Rocket To e Mark Faust Academic Adviser Andrew Greenberg Industry Sponsor Capstone Team Members e Sarah Bailey Computer Engineering Jacob Davidson Electrical Engineering Glenn LeBrasseur Computer Engineering 16 June 2006 Table of Contents 1 Introduction 2 Final Requirements 3 System Level Design 1 Communications Bus 1 Bus Requirements 2 CAN and USB Comparison 2 Microcontroller 1 Requirements 2 32 bit Microcontrollers considered 3 ARM Comparison 4 Final Choice 3 RTOS 1 eCos 4 System Block Diagram 1 Block Diagram of Node 2 Switching Power Supply SPS Block Diagram 3 ARM and Glue Circuitry Block Diagram 4 Detailed Design 1 Schematics 1 Eagle CAD Schematic of node 2 Board Layout 5 Component Specification 1 SPS Front end Passive Block Circuit Breaker Block Overvoltage Protection Switcher Secondary Voltage Supply Power LED Bill of Materials BOM 2 ARM and Glue Circuitry NOOR OD 1 ARM 7 microcontroller U280 2 Power decoupling C285 286 287 288 291 292 3 USB filtering block 4 Power on reset 5 Oscillator and divider 6 RTC crystal oscillator 7 Debug port 8 Power Good and Shutdown 9 Breakout of signals to application specific area 10 Status LEDs 11 Test points 12 Configuration trace cuts or solder jumpers 13 Bill of materials BOM 6 Software 1 Int
29. RQFR82V MCR10EZHF4702 MCRI10EZHF1822 Order Size Shielded Drum Bobbin SMT 0 35 0 56 1 04 0 36 0 89 0 38 0 38 0 38 0 38 0 38 0 38 0 38 0 38 3048 4521 2755 4177 896 34 300 3370 960 760 15560 3160 4440 6840 3650 0805 1206 SOT 23 SOT 23 SMB 0805 0805 0805 0805 0805 0805 0805 0805 0805 pas 1 10 10 10 10 10 10 10 10 10 5 2 ARM and Glue Circuitry 5 2 1 ARM 7 microcontroller U280 Part Description e LPC2148FBD64 S ARM 7 TDMI 16 32 bit microcontroller 64 pin LQFP package Purpose e This is the computational resource on the node board and facilitates communications between application specific sub systems on the node and the avionics communications bus using the USB Specifications Calculations e The detail of specifying this component is provided on the CapstoneLV2bProjectReport Microcontroller page e User manual of the Philips LPC2148 is at http www semiconductors philips com acrobat_download datasheets LPC2141 42 44 46 48 1 pdf 5 2 2 Power decoupling C285 286 287 288 291 292 5 2 2 1 C285 C286 C287 C288 C291 C292 Part Description e 10 nF 50 volt Chip X7R 0805 package Panasonic ECJ 2VB1H103K Digikey P N PCC 103BNCT ND http www panasonic com industrial components pdf abj0O000ce1 pdf Purpose e Local transient suppression at chip Pre
30. a where Prota Vin linavg Pioaa Piosses where Pioad Vout load and Piosses are the losses internal to U200 We can measure the average input current linavg using a Current probe 7 2 ARM and Glue Circuitry 7 2 1 Reset Circuitry e Objectives o Verify RESET signal is asserted upon power up o Verify RESET is released tRPU after Vdd exceeds Virip Fig MCP130 1 1 o Verify RESET remains non asserted while APS maintains load regulation within spec Fig MCP130 2 2 Components needed to be installed o Entire SPS subsystem o U283 7 2 2 Crystal Oscillator e Objectives o Verify crystal oscillator always starts o Verify crystal circuit oscillates at the correct frequency o Observe variation in frequency drift o Verify oscillator signal has an acceptable wave shape o Verify oscillator is being divided down to the correct frequency for SPS Sync Components needed to be installed o Entire SPS subsystem o U280 ARM chip o X281 12 0 MHz crystal o U281 7 stage divider 7 2 3 USB interface e Objectives o Verify endpoint enumerates o Verify data is transmitted without error Components needed to be installed o Essentially everything on the schematic 7 2 4 ARM Glue power up e Power up sequence o t0 DC applied o t1 MAX5902 release soft start o t2 C201 charges up o t3 LT1767 starts operating o t4 2 6 V on output of SPS o t5 LPC2148 Oscillator starts o t6 3 0 V on output of SPS o tZ
31. ackage size available was a 168 pin BGA 3 2 3 ARM Comparison The capstone team searched the websites of over 34 companies that license the ARM core Of those companies only five had microcontrollers with CAN or USB Atmel Freescale Philips STMicroelectronics and Texas Instruments There were roughly 30 chips that met our requirements We compared the 30 chips looking at various characteristics such as package size speed memory and peripherals For the full comparison chart see the file NodeMicrocontrollerSearch ARMs xls There were 11 microcontrollers that best met our requirements 5 had both CAN and USB 3 had CAN only and 3 had USB only The microcontrollers that had both CAN and USB were all 100 pin packages from Atmel Once we looked at drawings of pin package sizes compared to our required board size we realized that we simply couldn t fit a 100 pin package on the board That only left the 64 pin CAN only or USB only microcontrollers When the decision was made to use USB in the next generation rocket we took a look at the USB only ARM chips There were three top choices an Atmel AT91SAM7S256 the Philips LPC2148 and the STM STR711FR2T6 3 2 3 1 Comparison Chart Characteristic Atmel Philips STM production status production sampling active SRAM KB 64 40 64 flash KB 256 512 256 frequency MHz 55 60 66 JTAG Y Y Y serial boot N Y A D bits 10 10 12 number of ADCs 8 14 4 max number of GPIO pins 32 45 30 UART
32. al circuit Figure Glue 3 illustrates the relationship between circuit voltage and the suppressing current capability EQUIVALENT SCHEMATIC DIAGRAM Aort Bor D One Suppressor Shown NOTE All GND terminals should ba connected to ground Image from TI SN65220 datasheet Fig Glue 2 CURRENT vs VOLTAGE TS 25 25 Current A 5 75 10 10 5 o amp 10 16 Voltage V NOTE A Typical currant versus voltage curve was derived using tha IEC 1 2 50 us surge wavelarm Image from TI SN65220 datasheet Fig Glue 3 5 2 3 5 EMI RF Filter L281 L282 Part Description e Chip EMI Filter Type EXCCET Package C type Panasonic EXC CET471U Digikey P N P9829CT ND http www panasonic com industrial components pdf AEHOOOOCE3 pdf Purpose e To suppress RF signals that may be picked up on the external USB bus and still pass the baseband USB signal Specifications Calculations e This component provides RF attenuation on the USB circuit as shown in Figure Glue 4 The baseband USB signal is 12 Mb sec giving a worst case frequency alternating 1010 pattern of 6 MHz In order to to attenuate this signal the device number 471 in Figur Glue 4 should be chosen This gives a maximum attenuation of about 38 dB at approximately 150 MHz This maximum attenuation frequency is useful in another respect since we use 146 MHz VHF communications for another avionics subsystem Note 6 in the data sheet mentions the device deteriorate
33. ansient Duration SUPPLY VOLTAGE TIME Ed _ b e above the A cue a reset Bites Transients below 2 the curve will ie tae cause a reset TRANSIENT DURATION us VTRIP VoD W Image from Microchip MCP130 datasheet Fig Glue 5 Image from Microchip MCP130 datasheet Fig Glue 6 5 2 5 Oscillator and divider e The crystal based system oscillator is described in the Philips User Manual in chapter 3 This oscillator and divider block provides two functions to the node First it is the primary system clock for the LPC2148 microcontroller and second it is a synchronizing oscillator for the SPS The oscillator amplifier is internal to the LPC2148 with output appearing on X2 pin 61 and input on X1 pin 62 The microcontroller internally uses the output of the amplifier to operate it s logic clock circuits Fig Glue 7 shows the schematic of this functioal block X1 X2 Fig Glue 7 5 2 5 1 Frequency control crystal X281 Part Description e 12 MHz Surface Mount Crystal Fundamental Mode CS10 package 6 0 mm x 3 3 mm Citizen CS10 12 0000MABUJTR Digikey P N 300 8089 1 ND http dkc3 digikey com PDF T062 0941 pdf Purpose e The system clock is driven by an internal oscillator amplifier using an external crystal for frequency reference This crystal is the primary frequency determining component of the oscillator The resonant circuit formed by this crystal is in the feedforward pa
34. ay given that U251 does not shutdown during these transients See C250 Specifications Calculations e We wanted C251 to filter transients which lasted less than 100 us therefore we need to find the output resistance C251 sees under a transient or AC condition We used the zero time coefficient technique to solve for the resistance and eventual capacitance Under a transient condition the SPS output and comparator output are grounded DC voltage and removing C251 the resistance it sees is the parallel combination of R254 and R255 R254 R255 6 46 kohm with an RC 100 us we can solve for C 15 4 nF The closest standard value is 0 015 uF The voltage rating needs to be greater than 20 V just for safe measure 5 1 4 Switcher 5 1 4 1 Step Down Switching Voltage Regulator Buck Topology U200 Part Description Main SPS Switching Buck Regulator at 3 3V rail and lo max 400 mA Monolithic Step Down Buck Switching Regulator Current Mode Control 1 5 A 1 25 MHz Adjustable 3V lt Vin lt 25 V 8 MSOP No exposed ground thermal pad ROHS Non Compliant Linear Technology LT1767EMS8 Digi Key p n LT1767EMS8 ND 6 00 1 http www linear com pc downloadDocument do navid H0 C1 C1003 C1042 C1032 C1064 P1915 D1885 Purpose This is the switching voltage regulator It specifically is a buck topology which uses current controlled loop control and has adjustable voltage at the output Specifications Calculations We wan
35. ck Another low dropout LDO regualtor could possibly further regulate its voltage down to 5 V since it will not be 5 V This block is included in the SPS design because certain nodes in the LV2b will use parts specifically analog to digital converters ADC which are 5 V parts This secondary buck regulator will regulate the tapped Switcher voltage down to something around 7 2 V which again can be regulated be a LDO for the ADC s use 3 4 3 ARM and Glue Circuitry Block Diagram The underlying goal of the Glue subsystem is to satisfy the interconnection needs of the microcontroller and to provide any forseen resources to the application specific area for future users Shutdown Sync Power Good System Block Diagram Glue ARM7 microcontroller CPU e This is the ARM7 microcontroller that is the primary processor on the node The microcontroller contains 10 bit analog to digital converters a digital to analog converter pulse width modulators general purpose I O external interrupts SPI interfaces 1 2 C interfaces 2 UARTs counters timers PLLs and a USB interface The ARM7 core runs at 60 MIPS has 40 K Bytes of RAM and 512 K Bytes of flash memory There is a JTAG Joint Test Action Group debug port The flash memory can be programmed through one of the UARTS Power decoupling e This block provides transient decoupling between switching power supply and the logic power The block also provides a single point ground connec
36. d that if the 3 3 V SPS output was to reach 3 5 V we would want this to qualify as an overvoltage trigger event Since we have been using several 10 0 kohm resistors we specified R255 to be 10 0 kohm Therefore using the overvoltage trigger event value to be 3 5 V and the compared voltage to be 1 242 V we solved for R254 1 242 V 3 5 V R255 R255 R254 and solving for R254 18 18 kohm The closet standard value was 18 2 kohm 5 1 3 4 2 R255 Part Description e 10 0 kohm 0805 1 1 8 W Cut Tape ROHS Compliant Rohm MCR10EZHF1002 Digi Key p n RHM10 0KCCT ND 0 38 10 http www rohm com products databook r pdf mcr10 pdf Purpose e R255 along with R254 form a voltage divider with respect to the 3 3 V SPS output rail When there is an overvoltage at the 3 3 V SPS output the voltage at the IN pin pin 4 of U251 will be greater than the internal reference voltage of U251 typically 1 242 V and will result in the comparator in U251 outputing a logic high value When the SPS output is below a certain threshold the input voltage pin 4 to U251 is less than the internal reference voltage and the comparator s output is a logic low Specifications Calculations e We specified R255 10 0 kohm See R254 5 1 3 5 TLV3012AIDBVT Secondary Power Supply Schottky Diode CR250 Part Description e 30V 1 5A 4ns New MiniPower 2P Cut Tape ROHS Compliant Panasonic SSG MA2Q70500L Digi Key p n MA2Q70500LCT ND 0 83 1 h
37. de a limited amount of guaranteed bandwidth 10 of the frame or more if the isochronous transfers take less than 90 of the bandwidth They are acknowledged by the receiver and automatically retransmitted if the message was not acknowledged or if it was corrupted Control transfers would be ideal for system critical messages such as data from the DTMF receiver board or commands to the recovery node Each USB endpoint could be set to a different transfer type 3 1 2 2 2 Connectivity A USB communications bus could be directly plugged into a software developer s laptop CAN requires special conversion hardware such as USB to CAN adapters to interface with a laptop USB will require a special connector since the standard connector does not lock into place However CAN has no standard connector so we will be creating our own custom connectors anyway 3 1 2 2 3 Firmware and Device Drivers The most likely candidate for an open source RTOS is eCos and the flight computer will run Linux PSAS members have experience writing CAN drivers but they also have local contacts with people who write Linux USB device drivers There are many Linux and eCos USB drivers available that could be modified but few CAN drivers Linux and eCos both have a hardware independent driver framework for USB but not for CAN PSAS members have written CAN drivers and PSAS has contacts with programmers who have written USB drivers for Linux Even if we find a device dri
38. de by side as suggested in the schematic but are offset and superimposed on top of each other on the same side of the PCB Because only one cap will be used we offset the pads such that they are not directly on top of each other and either package can be placed down thus saving space The values are TBD 5 1 6 Power LED 5 1 6 1 SPS Output Power On LED D201 Part Description e 1 9 V 90 mcd 20 mA 609 nm 0805 Orange Diffused LED CML Innovative Technologies Inc CMDA5BA7D1S Digi Key p n L71515CT ND 3 00 10 http www chml com pdf temp CMDA5BA7D1S pdf Purpose e This is an orange LED which is lit given that the nominal SPS 3 3 V rail is up It is mainly used as an initial indicator of the 3 3 V rail s status Orange was an arbitrary choice however any other LEDs in the Glue Logic section needed to be different colors The intensity and viewing angle are not critical since the only time the information from the LED is useful is in trouble shooting on the ground It remains lit throughout the whole flight Specifications Calculations e From the CMDA5BA7D1S datasheet Vf 1 9 V We specified the LED drive current to be 2 mA See R214 for l V calculations 5 1 7 Bill of Materials BOM NOTE Component fields with a mean they are TBD 5 1 7 1 Digi Key BOM Qty Digi Key SKU Cust ID Part Mfgr 5 LT1767EMS8 ND o U200 Linear Tech 5 PCC2401CT ND hg C200 Pansonic ECG 5 PCC2414CT ND nr C201 Pansonic ECG 5 PCC1840CT
39. digikey com WebLib BC 20Components Web 20Data MLCC 20SMT 20NPO 20 10 16 25 20 26 2050V pdf Purpose e This cap is a noise bypass cap to the SHDN pin of U200 Specifications Calculations e We specified a 0 1 uF standard value bypass cap 5 1 4 4 Buck Input Cap C201 Part Description e 10uF 25 V 1206 X5R Cut Tape ROHS Compliant Panasonic ECG ECJ 3YB1E106K Digi Key p n PCC2414CT ND 5 45 10 http www panasonic com industrial components pdf abj0000ce4 pdf Purpose e C201 is the input cap to U200 Specifications Calculations e From page 7 in the LT1767 datasheet we used the formula to calculate the rms ripple input current Irms lo sqrt Vout Vin Vout Vin 2 Given that the unlikely transient worst case power bus supply current drawn by the SPS is lo 1 A Vin 20 V and Vout 3 3 V we can solve for Irms 1 A sqrt 3 3 V 20 V 3 3 V 20 V 2 371 mA The ripple voltage is equal to dV Irms dt C201 where T 1 f 667 ns The ripple voltage at the input is not too critical given that it is much less than a few volts in magnitude which could trigger the SHDN pin of U200 Other than that the only other problem is that if the current through L201a b is constant and there is a sudden step in the current draw the voltage across C201 could possibly become greater than the power bus voltage There even is potential of ripple voltage actually aiding U200 efficiency where the rippl
40. e also on top and bottom The decision to use only two trace layers was driven by the desire to use the free version of Eagle CAD which is a PSAS standard On the left top side of the board is the USB Power connector The Debug port will be placed on the left bottom side Top side only of board Bottom side only of board 5 Component Specification 5 1 SPS SPS Design Schematic rev2 2 pdf Note It is easier to refer to the schematic above when reading section 1 5 1 instead of the detailed Eagle schematic in section 1 4 1 1 This is because this section exclusively covers all SPS components The part numbers are consistent with those in the Eagle schematic 5 1 1 Front end Passive Block 5 1 1 1 Power Bus Input Choke L201a L201b Part Description e CMS1 11 R Common Mode Inductors 100 uH Micro PAC Plus Package RoHS Compliant Tape and Reel http www cooperet com library products PM 4313 20CMS Series pdf Purpose e Common mode choke balanced inductor It is used as an EMI filter between the power bus and the SPS Specifications Calculations e The value was chosen through a trial and error process from the pervious LV2 SPS design Each inductor of the choke is 100 uH See page 13 of the CAN Node Switch Mode Power Supply SPS 200 section in the Component Design for LV2 Power Electronics Except Main Battery engineering design notes 5 1 1 2 Power Bus Fast Acting Fuse F200 Part Description e 50
41. e reconfigured by doing a physical trace cut and resolder The configuration changes are for analog reference voltage source and clock battery voltage source 4 Detailed Design 4 1 Schematics 4 1 1 Eagle CAD Schematic of node The schematics used in the design of this project appear in two forms one for the Spice circuit simulator and another for the Eagle CAD PCB board layout tool This section only shows the Eagle CAD schematic The Spice schematic was used for verification of the SPS design and can be found in that section gagpongcgmasnge i a Squat TITLED nodes ing a TETIT E CW Rne Certed Docunent Musber AA COI Oh 1 Ret eR dene OD terre Cet Date 6 10 2005 14 52 27 e get view 290 6 KB attachment gnl_schem png e get view 160 6 KB attachment gnl_schem_small png 4 1 1 1 Naming convention The name of this project according to PSAS convention is e node4 USB Node V4 which is the ARM7 SPS v2 2006 capstone design So the name of this board is v2 node4 frontend 4 1 1 2 Getting the Eagle CAD board layout tool Go to the Eagle CAD site http www eagle de and follow the instructions under downloads for your specific platform For this project we used the Debian Linux distribution and thereby were able to use Debian s package management tool called Aptitude The following command on a Debian Linux system installs the Eagle CAD software package s
42. e steady state currents in the range of 400 mA to 500 mA qualify as an overcurrent event and should be detected To avoid wasting power dissipated by Q250 s RDS on and R252 those values should be kept low therefore the voltage across them should also be low and the 300 mV threshold version satisfied that Upon power up U250 keeps Q250 off and if trigger events 1 and 2 are non existent then it gradually turns Q250 on to saturation in approximately 150 ms The drain of Q250 is gradually enhanced at a rate of about 9 V ms This start sequence limits the inrush current giving some soft start protection to its load Once all transients are gone before the 150ms time period and Q250 is fully saturated U250 s circuit breaker functionality comes up and monitors the Vds of Q250 between pins 1 and 2 Before this initial power up 150 ms period there is no circuit breaker functionality If any one of the 4 trigger events occurs U250 will turn Q250 off de assert PGOOD output a logic high and reinitiate the start sequence given that the trigger event s disappears during the 150 ms period if not the 150 ms period will repeat There are two typical turn off times regarding Q250 10 ms and 4 us If there is an ON OFF or UVLO trigger event they need to exist for 10 ms before U250 turns Q250 off which will take an unspecified amount of time If there is an overcurrent or temperature trigger event then Q250 is turned off in 4 us If the trigger events di
43. e voltage could possibly increase the duty cycle of U200 Given the reasoning s above the ripple voltage is not too much of a concern Therefore we just want a bigger cap in size 1206 and value such that it can act as a temporary voltage supply to U200 under slightly larger current loading We chose to use a 10 uF cap in a 1206 package The ripple voltage then is dV Irms dt C201 871 mA 1 f 10 uF 24 7 mV This is negligible Since this is a high frequency node C201 and CR200 will be closely grounded together 5 1 4 5 LT1767 Frequency Compensation Caps C205 C206 5 1 4 5 1 C205 Part Description e TBD Purpose e Part of the frequency compensation of U200 Specifications Calculations e See pages 24 25 of the CAN Node Switch Mode Power Supply SPS 200 in the Component Design for LV2 Power Electronics Except Main Battery engineering design notes Also see pages 48 50 of the Linear Technology application note an 19 and see application note an 76 The value is TBD C205 may not be needed given that the frequency compensation of R206 C206 is satisfactory 5 1 4 5 2 C206 Part Description e TBD Purpose e Part of the frequency compensation of U200 Specifications Calculations e See pages 24 25 of the CAN Node Switch Mode Power Supply SPS 200 in the Component Design for LV2 Power Electronics Except Main Battery engineering design notes Also see pages 48 50 of the Linear Technology applicatio
44. eb and its magnitude is dependent on the value of R253 and the bus voltage at the time nominal value of 16 8 V When there is no overvoltage at the 3 3 V SPS output U251 outputs a logic low thus keeping Q251 off Specifications Calculations e Since the gate of this FET would be driven by the output of a comparator in U251 it would be best for the FET to be a logic level device Other concerns was for the drain source breakdown voltage to be higher than 30 V as the highest possible DC value the bus voltage rail would be is 20 V 5 1 3 4 TLV3012AIDBVT UVLO Lockout Resistor Network R254 R255 5 1 3 4 1 R254 Part Description e 18 2 kohm 0805 1 1 8 W Cut Tape ROHS Compliant Rohm MCR10EZHF1822 Digi Key p n RHM18 2KCCT ND 0 38 10 http www rohm com products databook r pdf mcr10 pdf Purpose e R254 along with R255 form a voltage divider with respect to the 3 3 V SPS output rail When there is an overvoltage at the 3 3 V SPS output the voltage at the IN pin pin 4 of U251 will be greater than the internal reference voltage of U251 typically 1 242 V and will result in the comparator in U251 outputing a logic high value When the SPS output is below a certain threshold the input voltage pin 4 to U251 is less than the internal reference voltage and the comparator s output is a logic low Specifications Calculations e From the LPC2148 datasheet the maximum supply voltage it can handle is 3 6 V therefore we specifie
45. ectory You can check that eCos has found the repository by seeing if the GPL GPS template is available Go to Build gt Templates In the first drop down menu scroll down through the available templates If you see the GPS 4020 template eCos has access to the CVS repository 6 3 Serial Port Test Software needed e minicom To check that the LPC2148 is communicating over the serial port first you need to set up minicom Start minicom up with minicom s This brings you to the setup menu Go to Serial port setup to change some settings Type A to change the serial device used a USB to serial adaptor in Linux so set up my output port to be dev ttyUSBO Make sure hardware and software flow control are both set to No Type E to set the Bps parity and stop bit You should configure it for 8 data bits 1 stop bit no parity and 38400 Bps Once minicom is configured save the setup and exit to minicom Type CTRL A A to add a linefeed to the data the LPC2148 expects a carriage return followed by a linefeed at the end of every commana Once minicom is setup and running follow these steps 1 Send the synchronization character Wait for the board to send back Synchronized Send Synchronized back Board will send back OK Now the board is waiting for the frequency in kHz for the crystal oscillator on the board 12000 is correct for the Olimex board ao fF wo NM 6 Board will send back OK if synchro
46. efault is to use SPS power To use the alternate sourde cut the fine trace between the default pads and reconnect the alternate with a solder bridge 5 2 13 Bill of materials BOM Following are the components needed to construct the Glue section of the board Qty tS 10 The quantity is the number of individual pieced needed This number may need to be increased to fit the minimum order size The first three columbs are Digi Key Fast Add order format fields provided the quantiny is properly adjusted Digi Key SKU 568 1765 ND 296 12760 1 ND 296 9694 1 ND MCP130T 315I TTCT ND 300 8089 1 ND 300 8193 1 ND PCC390CGCT ND PCC330CGCT ND PCC220CNCT ND Cust ID PSAS GLUE PSAS GLUE PSAS GLUE PSAS GLUE PSAS GLUE PSAS GLUE PSAS GLUE PSAS GLUE PSAS GLUE PSAS GLUE PSAS GLUE Part U280 U281 U282 U283 J281 J282 X281 X282 C281 C282 C283 284 Mfgr Philips TI TI Microchip JST JST Citizen Citizen Panasonic Panasonic Panasonic Description ARM7 Microcontroller 7 stage CMOS ripple counter USB port transient suppressor Microcontroller Supervisory Circuit 12 MHz Surface Mount Crystal Fundamental Mode 32 768 kHz Surface Mount Crystal Tuning Fork Chip NPO 39 pF Chip NPO 33 pF Chip NPO 22 pF Mfg Num LCP2148FBD64 S CD4024BPWR SN65220DBVR MCP130T JST 08PS
47. es The PLL lock time also seemed to be a bit long it was listed as 600us while Philips listed a 100us lock time Further the internal oscillator takes 2 5 seconds to start up If the microcontroller has to do a hard restart in flight we would lose half of the apogee window to oscillator initialization Also the data sheet was vague about whether the internal voltage regulator could be bypassed in Standby mode 3 2 3 3 USB Considerations The STM documentation for USB was severely lacking Their datasheet did not indicate how many of each type of USB endpoint were available The lack of documentation made this an unacceptable choice The Atmel part only had four USB endpoints two endpoints could be configured to be isochronous endpoints They also listed endpoint 0 as being able to send control bulk or interrupt transfers This seemed to be an indication they were doing something out of spec with their USB controller since the USB specification clearly states that endpoint 0 must be reserved for control transfers from the host The Philips chip had the best documentation of the three chips and it had the most endpoints The LPC2148 had 16 USB endpoints and 4 endpoints could be configured to be isochronous endpoints 3 2 4 Final Choice In the end we decided to choose the Philips LPC2148 chip because of its great documentation and USB support 3 3 RTOS A program with real time requirements will need a real time operating system
48. ex board to on and plug the serial cable from RS232_0 on the Olimex board to your computer Power cycle the board Now you ll want to send the program to the Olimex flash memory lpc21isp will write a flash block s worth of the program to RAM then burn that to flash To send the main hex file to the Olimex board run the following command lpc2lisp debug hex PHILIPSARM main hex dev ttyUSBO 38400 12000 The debug flag tells the program to print out debug statements The nex flag means the program should expect a hex file to send and the px1L1Psarm flag means we re sending to a Philips chip main hex is the file to send and dev ttyusBo is the port to send it over was using a USB to serial adaptor so used the Linux specific path that pointed to that USB device If you re using Windows or a serial port on your computer you ll need to replace dev ttyUSBO with the OS specific path usually com1 for serial in Windows The program will write bits across the serial cable for a couple minutes Once the program is done you ll see Download Finished followed by a message that it s launching the new code Launching from the software doesn t work You ll need turn switch 1 off and push the reset button Then you should see LED1 blinking away 6 4 6 Results The program worked as intended and the LED attached to P0 10 blinked constantly The author intended it to blink once a second and it blinks a little slower than that There is
49. ges at the nodes mentioned earlier When these nominal voltages are noted we will apply a varying load at the output and measure the voltages again This will give us an idea about how much current we can draw before the loading effect is too much These values will help specify a LDO 7 1 5 2 Cross regulation of dual voltage supplies what effects do each have on the other e Objectives o Along with the mutual coupling of L200a and L200b we want to observe the dependencies between the two 3 3 V and 5 V voltage rails as loads are varied and as the SPS recovers from one of the four fault events Equipment o Various resistors and potentiometers o Oscilloscope o Current probe o Spectrum Analyzer maybe Experiment o With the whole SPS including a LDO at the output of the secondary supply operating nominally we will vary the load at one supply output and view the transients at both outputs We will then do the same for the other then we will vary the loads at both supply outputs and view the transients This will be a trial and error process to extrapolate the dependencies 7 1 6 Final System block testing 7 1 6 1 Maximum system current flow e Due to Inductor inductor saturation temperature w and w o circuit breaker e Objectives o There could actually be several maximum output currents meaning the inductor could saturate at a certain output current U250 could trip at a different current F200 could blow at another cur
50. he LPC2000 prohibits users from posting copyrighted works in their files sections saying Do not upload any copyright material to the group s Files area It will be deleted and the offender banned from the group The file remains and Philips Marketing Team has not been banned from the group which leads me suspect no one assumed the license was valid 6 4 3 Modifications From Original If you re a Linux user change this line in main c include lpc2141x h to include LPC2141x h The header file is misnamed in the top line This bug doesn t show up for Windows users because Windows is case insensitive Also he got some bit math wrong in demo2148_blink_flash cmd ram_isp_low A ORIGIN 0x40000120 LENGTH 223 should change to ram_isp_low A ORIGIN 0x40000120 LENGTH 224 This bug won t affect the blinky LED demo since it doesn t take up a lot of room in RAM The Makefile is created for the arm elf tool chain so you ll have to change the lines that start with CC Change the gcc compiler to arm linux gnu gcc and the rest from arm elf to arm linux 6 4 4 Source Code Review File usage e pc2148 led_demo cmd defines the memory map for the LPC2148 e crt s start up assembly code e LPC214x h GPIO addresses e main c initialization of the system endless toggling of the LED 6 4 4 1 Code Snippet main c int main void Initialize the system Initialize Hi ear ie ime
51. ider for U200 Along with R210 this resistor divider ensures that U200 does not regulate until after a turn on threshold voltage level has been met Specifications Calculations e The UVLO voltage was specified to be 9 V See page 10 and Figure 4 in the LT1767 datasheet Letting R210 10 0 kohm and VH 9 V the UVLO formula from page 10 in the datasheet is R210 1 33 V VH 1 33 V R209 3 uA and solving for R209 59 kohm The closet standard value was 60 4 kohm 5 1 4 2 2 R210 Part Description e 10 0 kohm 0805 1 1 8 W Cut Tape ROHS Compliant Rohm MCR10EZHF1002 Digi Key p n RHM10 0KCCT ND 0 38 10 http www rohm com products databook r pdf mcr10 pdf Purpose e This is a part of the UVLO resistor divider of the LT1767EMS8 U200 Along with R210 this resistor divider ensures that the LT1767EMS8 does not regulate until after a turn on threshold voltage level has been met Specifications Calculations e The UVLO voltage was specified to be 9 V See page 10 and Figure 4 in the LT1767 datasheet Letting R210 10 0 kohm and VH 9 V the UVLO formula from page 10 in the datasheet is R210 1 33 V VH 1 33 V R209 3 UA and solving for R209 59 kohm The closet standard value was 60 4 kohm 5 1 4 3 LT1767 UVLO Resistor Network Shunt Cap C210 Part Description e 0 1 uF 50 V 0805 X7R Cut Tape ROHS Compliant BC Components VJO805Y104KXATW1BC Digi Key p n BC1298CT ND 0 72 10 http rocky
52. ified amount of time in case the magnitude of the voltage change of a transient causes a trigger event but lasts a very short amount of time or would normally shut down U251 thus avoiding the time needed for U251 to power cycle When the overvoltage at the SPS output event occurs there is a finite amount of time required before Q250 is eventually turned off namely the propagation delay of the comparator in U251 the turn on delay time of Q251 the time to turn off Q250 by U250 and the turn off delay time of Q250 These typical times as are 12 us 8 ns 4 us and 26 2 ns as specified on pages 3 3 8 and 4 in the TLV3012 BSS1223 MAX5902 and ZXMP6A17E6 datasheets respectively resulting in an ideal propagation delay of about 17 us After these propagation delay times Q250 is off and the input voltage Vin pin 2 of U200 is zero volts after C201 is discharged triggering the SHDWN pin and turning off U200 When this happens the power supply to U251 is essentially removed so the time constant for C250 has to be long enough such that as U250 is going through its start sequence 150 ms the comparator in U251 can output a logic low and turn Q251 off as the voltage it is comparing IN pin 3 to its internal reference voltage REF is the divided see R254 R255 SPS output rail voltage which at this time is zero volts To make sure that this sequence of events happen we specified U251 to have power long enough to turn Q251 back off while U250 is turning back
53. in P0 10 and P0 11 are outputs bit 11 and 10 set 0 1100 0000 0000 0xC00 FIOOSET 0x00000400 P0 10 led off FIOOSET 0x00000800 ee Ot MEG ott FIOOCLR 0x00000400 P0 10 led on FIOOCLR 0x00000800 P0 11 led on 6 5 3 1 Comments This code is much cleaner and simplier than the non eCos code The blinky c code was 21 lines long whereas the non eCos main c code was 168 lines of code much of that initialization code The eCos compiled code size is bigger than the non eCos code size because of the linked eCos code Here is a comparison of the code size in bytes obtained using arm linux gnu size code type text data bss dec non eCos demo 788 24 28 840 eCos demo 24808 844 17044 42696 The eCos demo is 42KB The program resides in flash memory on the LPC2148 but parts of it will be loaded into RAM at run time The LPC2148 has 32KB RAM and 512MB flash so that still leaves enough room for future software development 6 5 4 Compiling the eCos Demo Once you have patched your eCos repository with Pawel s patch see the RTOS section you re ready to build the eCos program First download the tarball LPC2148Software lpc2148 ecos tgz Extract it with tar xvzf lpc2148_ecos tgz in whatever directory you want Change to the lpc2148_ecos directory and run configtool Open lpc2148_rom ecc by choosing File gt open Then create the eCos source tree by choosing Build gt Generate Build Tree Once that has finished cho
54. iscontinuous mode Equipment o Various resistors and potentiometers o Oscilloscope o Current probe Experiment o We will load the output and sweep its value until the U200 enters saturation mode We will record the output current at which this happens if it does at all We will then measure the voltage and current across and through L200a L200b respectively when there is zero current draw 7 1 3 2 Minimum output voltage for the minimum on time of U200 e Objectives o We want to vary Vin to change the duty cycle and hence the on time of U200 and notice the SPS output voltage behavior Equipment o Voltage source o Oscilloscope o Current probe Experiment o The duty cycle D of a switching voltage regulator is D Vout Vp Vin Vsw Vp where Vour is the SPS output voltage Vin is the power bus voltage Vsw is the voltage drop across the 0 22 ohm switch resistance in U200 and Vp is the voltage drop of CR200 The ON time ton of the regulator is toy D f where f is the 1 5 MHz switching frequency of U200 7 1 3 3 Frequency compensation testing amp component selection e Objectives o The frequency compensation will help regulate the SPS output voltage by limiting the bandwidth of the error amplifier and hence the switching frequency of the internal switch in U200 We can help control the amount of ringing at the output Equipment o Various resistors potentiometer o Some NMOSFETs o Various active com
55. ithium ton Batteries PowerPC Flight Computer 400MHz MPCS200 603e core wi tZ3MB SORAM IZME flash CAN ethernet and USB unning Debian Lux 26x Power System Board Ea opm Maxim MAX1168 16bit ADC Smari battery charging and monitoring E channels 200ksp5 MOSFET power switches to subsystems Philips LPC 2148 Microcontroller Philips LPC2148 Microcontroller GOMHZ 22 Dit ARM uC with USB running eCos GOMHZ 32 bit ARM uC with USE running eCos Universal Serial Bus USB v1 1 Telemeti Amateur TV GPS Philips LPC2148 Microcontroller Philips LPC2148 Microcontroller Philips LPC2148 Microcontroller 6BOMH 32 bit ARM uC with USE running aCos 6OMHz 32 bit ARM uC wan USB running eCos GOMHz 32 bil ARM uC with USE running aCos sA UART UART Nordic nRF24L01 2 4 GHz Transciever 1GB USB Color Camera Video Overlay Board GPL GPS Open Source GPS Receiver 2 MBps 0 GBm output 85 dBm input GFSK modulation flash disk NTSC Audio out NTSC Serial text in NTSC out 12 channei COTS board with OSS firmware 2 4GHz Bidirectional Power Amplifier 1 253GHz FM Amateur TV Transmitter 1 575GHz Low Noise Preamp YFI inc 1648 Transmit 608 Receive 1SmW output GPS Source 3008 preamp with SAW fiters ai 1 25GHz Class C Power Amplifier IW output Recovery Philips LPC2148 Microcontroller GOMHZ 32 bit ARM uC with USB running eCos Back up Power Pyrotechnic System 41V Lithium ion 10
56. lo is the secondary output current of the SPS Vin is the voltage at the node which is between L200a and L200b and Vout is the SPS secondary output voltage We assumed that Vin would be switching somewhere between 1 6 V and 7 V With Vout 5 V and using the worst case lo 1 A and Vin 7 V values Id avg 286 mA again this diode is overrated We knew that not every node would need a secondary 5 V supply but even the ones that did the added current should not cause overcurrent events see U250 Hopefully 5 1 5 2 SPS Secondary Buck Output Cap C252 C252a Part Description e TBD Purpose e This cap along with CR251 and L200a form the second buck switching voltage power supply which will be eventually regulated down to 5 V possibly with a low dropout LDO linear voltage regulator These are application specific caps whose values are mostly independent from the SPS design Specifications Calculations e The only difference between C252 and C252a are the packages and that only one of them will actually be on the PCB Since we do not know any details about the actual application specific circuitry each SPS will power from an SPS design point of view we chose to use both a 0805 and 1206 package We chose two packages because we moved all relevant parts to the 0805 package from 1206 as in the LV2 SPS design and in case a specific application node needs a more beefy cap a 1206 package cap can be used The lay out of the parts will not be si
57. m SPS output current specified was 400 mA There are three circuit breaker threshold voltage versions of U250 300 mV 400 mV and 500 mV For certain reasons the 300 mV threshold part was chosen See U250 Therefore the Roson of the PMOS should be around 300 mV 400 mA 0 75 ohm We used a value of 1 ohm See R252 Even though the PMOS is used as a switch cutoff and saturation and not an amplifier cutoff triode and saturation we wanted to remove dependence of U250 s threshold voltage detection from the less precise Rps on of Q250 and to a more precise sense resistor Therefore we added a current sense resistor R252 in series with the drain of Q250 to produce a circuit breaker resistor Rcb which is the series combination of Q250 s Rps on and R252 between the two pins 1 and 2 of U250 We chose a PMOS with a low Rosin compared to the needed calculated value needed to trip the circuit breaker thereby making R252 close to Reb in value Therefore Q250 is used mostly as a switch and the voltage drop across R252 is used to trigger the switch See R252 The breakdown voltage of Q250 has to be greater than 20 V and should have a low turn on capacitance We do not care so much about the Vt but it does affect the turn on capacitance but these factors were not considered 5 1 2 4 MAX5902AAETT Circuit Breaker External P MOSFET RDS on Additional Series Resistor R252 Part Description e 0 82 ohm 0805 1 1 8 W Cut Tape RoHS Compliant Panas
58. m critical messages like commands for parachute deployment and manual overrides from ground support are important to retransmit if a failure occurs Retransmission of time based data like IMU readings is not useful and may eat up the bandwidth of the bus 3 1 1 2 2 Connectivity The bus should be able to interface to laptops during testing with minimal difficulty The communications connectors should be easy to remove during development and testing but must lock down during flight It would also be ideal if the node controllers could be flashed over the bus 3 1 1 2 3 Firmware and Device Drivers The firmware for the node controllers should be maintainable If there already exists tested bus protocol drivers it would be advantageous to use them to minimize the development time and design complexity Firmware and device driver development should not require proprietary software or a propriety environment i e Windows 3 1 2 CAN and USB Comparison 3 1 2 1 Avionics Team Requirements 3 1 2 1 1 Reliability Both USB and CAN are differential buses and are more immune to EMI than single ended buses CAN is used in some automobile systems but not in any systems where failure of the bus alone would result in an accident USB is used in some medical devices but not in life critical devices CAN and USB differ in how they prioritize messages CAN provides a message by message prioritization when the bus is idle and two nodes attempt to trans
59. mit the node with a higher prioritization continues to transmit and the other node waits for the bus to become idle USB allows the software to reserve bandwidth for each USB endpoint USB relies on a host in our case the flight computer to initiate all transactions even interrupts This means that if the flight computer powers off no messages will flow on the bus With the CAN peer to peer model the bus would still operate if the flight computer were offline 3 1 2 1 2 Performance CAN provides 1Mbps and full speed USB provides 12Mbps 3 1 2 2 Software Team Requirements 3 1 2 2 1 High Level Software Control The CAN controller handles packet retransmission automatically The Software team is concerned about the automatic retransmission of all corrupted packets Often we don t want an older time dependent message such as an IMU message to be retransmitted if it means that we don t receive the newest message If a high priority node starts sending lots of corrupted packets it may flood the bus with automatic retransmissions This is a remote possibility but it demonstrates the inflexibility of the CAN transmission protocol USB provides some flexibility when it comes to message retransmission If the transmitter uses isochronous transfers there is no ACK of the message and corrupted packets are not retransmitted Isochronous transfers provide guaranteed bandwidth and would be ideal for messages from the IMU Control transfers provi
60. n the target 1d file There was no references to the sections any any other code so we suspected it was a bug in the linker To make the linker happy we added this changed these lines in target 1id rom_ vectors 0x00000000 __ rom vectors_vma ABSOLUDE KEEP vectors gt rom __rom_vectors_lma LOADADDR rom_vectors text ALIGN 0x1 _stext ABSOLUTE PROVIDE __stext ABSOLUTE text gnu warning AT CAGMUrleinic lt on erie xn Gcumeitts mete Gacy lin Sma mca oui Smt e ro ete e PROVIDE Mere seen to rom vectors 0x00 000000 _ rom vectors_vma ABS OLUAE es es KEEP vectors gt rom __rom_vectors_lma LOADADDR rom_vectors TIOE ATTEN pth amp 5 aH eerie aerials Trom text ALIGN 0x1 _stext ABSOLUTE PROVIDE __stext ABSOLUTE text gnu warning onu LakiaicopoveKernic 6 ealioaiie ese 7 a Cotopll e fic J SS ron Sees Sop PROVIDE metet 5 Looking at the linker output the added sections only took up 4 bytes 6 5 3 Source Code Review To test the eCos port wrote a program to turn on two LEDs Here is blinky c in its entirety include LPC214x h include lt cyg kernel kapi h gt void Initialize void void feed void void cyg_user_start void Initialize the system set io pins tor led Por 10 SCS 0x03 select the fast version of the I O ports FIOODIR 0x00000C00 p
61. n note an 19 and see application note an 76 The value is TBD To find the value of R206 C206 Linear Technology suggested that this was a trail and error experimental process An experimental test circuit would vary the load at the output and the transient response of the output would be recorded namely the voltage ripple at the output For example in an experiment R206 is held constant and C206 is swept until a desirable output transient response is observed or vice versa where C206 is held constant and R206 is swept and then the constant parameter is stepped and another experimental sweep of the variable parameter is repeated The standard starting value for C206 is about 1 nF and is usually decremented 5 1 4 6 Boost Cap C202 Part Description e 0 1 uF 50 V 0805 X7R Cut Tape ROHS Compliant Panasonic ECG ECJ 2YB1H104K Digi Key p n PCC1840CT ND 1 61 10 http industrial panasonic com www data pdf ABJ0000 ABJOO00CE1 pdf Purpose e Boost cap C202 is connected to the BOOST pin pin 1 on U200 It is used to step up the voltage from Vsw pin 3 of U200 to drive the internal switch Specifications Calculations e The LT1767 datasheet recommends using a 0 1 uF film or ceramic cap with an ESR lt 1 ohm see page 9 The ECJ 2YB1H104K datasheet does not specify the ESR but states that this family of caps have a low ESL Also this same family of caps were used in the previous LV2 SPS 5 1 4 7 Boost Rectifier Diode CR201
62. nization occurs Otherwise it goes back to waiting for a synchronization character After these steps you can send any of the commands listed in Chapter 21 of the LPC214X User Manual A simple test that doesn t touch memory is to make the chip echo the microcontroller part number The command to send is J The LPC2148 should send back 67305253 6 4 Hello Blinky World Example Tools needed e Ipc2tisp e cross compiler tool chain Software needed e LPC2148Software lpc2148 led demo tqz 6 4 1 Introduction The source code for this demo was written by Jim Lynch The source code and tutorial can be found on this SparkFun thread http www sparkfun com cgi bin phpbb viewtopic php t 1331 6 4 2 License Issue The header file LPC214x h defines names for memory mapped addresses The header file was released by the USA Philips Marketing Team on the LPC2000 yahoo group http groups yahoo com group lpc2000 message 9444 The header file was part of a USB toolkit that Philips sold to consumers It has a rather nasty license referenced in it which says that you cannot use the header file in open source code or redistribute it anyone who hasn t agreed to licensing terms The Philips Marketing Team invalidated this license by posting the header file on public forum The header file is built on public knowledge and could be replicated by anyone with the LPC214x User Manual which further weakens the license s copyright claims T
63. no guarantee what the compiler will do with the delay loops so a better solution would have been to use an internal timer on the chip However for a simple demo this works fine 6 5 eCos Port Tools needed e Ipc2tisp e cross compiler tool chain e eCos Software needed e LPC2148Software lpc2148 ecos tgz contains o LPC214x h o blinky c o pc2148_rom ecc o Makefile o target ld 6 5 1 Introduction To get eCos running on a microcontroller a programmer must first create an eCos port for the microcontroller This includes a memory map initialization code a hardware abstraction layer HAL and more Typically an existing port for a similar processor can be modified but it still requires a lot of work 6 5 2 LPC2148 Port Fortunately Pawel Wodnicki has created a port for the LPC2136 8 and LPC2146 8 microcontrollers http sourceware org ml ecos patches 2005 11 msg00014 html The patch has not been merged into the CVS truck but it can still be used to patch the current eCos sources Download the patch into the ecos directory the original not the CVS repository Then type patch p1 ecos iH1 proc_lpc_1 patch There will be some warnings but they should be fine Once you have a patched eCos you can load Pawel s template for the LPC2148 Open configtool and go to Build gt Templates In the first drop down menu choose the template called Hobby Robotics iH 1_proc_lpc_1 board This was designed to work
64. on Pawel s evaluation board but it will work for any LPC2148 board 6 5 2 1 LPC2148 Port Modifications needed to make a couple configuration changes to compile under the arm linux toolchain The first fix was to change CYGBLD_GLOBAL_COMMAND_PREFIx to arm linux gnu Most of the other changes involved adding or removing compilation flags to make eCos build The difference in flags are probably due to using a newer gcc the eCos folks are still using gcc 3 2 whereas compiled with gcc 4 0 changed CYGBLD_GLOBAL_CFLAGS from mcpu arm7tdmi mno short load words Wall Wpointer arith Wstrict prototypes Winline Wundef Woverloaded virtual g O2 ffunction sections fdata sections fno rtti fno exceptions fv vtable gce finit priority to mcpu arm7tdmi mno short load words Wall npointer arith Wstrict prototypes Winline Wundef g 02 ffunction sections fdata Sections fno exceptions fv vtable gce ffreestanding fno use cxa atexit The flag ffreestanding wasn t strictly necessary but the flag fno use cxa atexit solved many of the compilation errors There were still linker errors so the CYGBLD_GLOBAL_LDFLAGS needed to be changed from mcpu arm7tdmi mo short load vorde W1l gc sections Wl static g nostdlib to mcpu arm7tdmi W1l gc sections Wl static g nostdlib The change of flags made some linker errors go away but the linker was still complaining that certian sections weren t i
65. onic ECG ERJ 6RQFR82V Digi Key p n P 82DCT ND 2 10 10 http www panasonic com industrial components pdf AOA0000CE3 pdf Purpose e This resistor dominates the circuit breaker resistor s Rcb value It is in series with the drain hence RDS on of Q250 to make up Reb The voltage drop across it is used to detect an overcurrent event given that it is greater than 300 mV See Q250 and U250 Note This value may change due to board level testing results Specifications Calculations e Since the typical value of Rps on of Q250 is 0 125 ohm and Rcb was about equal to 1 ohm R252 Reb Rogion 0 875 ohm The closet standard value was 0 82 ohm Given this value of Rcb and the circuit breaker trip threshold voltage of 300 mV the maximum SPS current which can be drawn before an overcurrent event is Imax 300 mV 0 125 ohm 0 82 ohm 317 mA which is under the specified maximum SPS current spec 5 1 3 Overvoltage Protection 5 1 3 1 Undervoltage Overvoltage Protection U251 Part Description e Nanopower Push Pull Output Comparator with Voltage Reference 1 8 V lt Vin lt 5 5 V SOT 23 6 Tape amp Reel TR ROHS Compliant Texas Instruments TLV3012AIDBVT Digi Key p n 296 16830 2 ND 262 50 250 NOTE Ordered samples from vendor no Digi Key http focus ti com lit ds symlink tlv3012 pdf Purpose e This comparator compares the specified divided SPS output voltage see R254 R255 to its internal reference voltage 1 2
66. ose Build gt Library The command won t finish due to errors from the target 1a file Replace target iain lpc2148 ecos lpc2148_rom_install lib with the target 1d file in the tarball found in the same directory as blinky c Then type make INSTALL_DIR TAR_DIR 1pc2148_ecos 1pc2148_rom_install where TAR_DIR is the directory where you extracted the tarball Now you should have a blinky hex file in the directory 6 5 5 Downloading Instructions Set switch 1 on the Olimex board to on and plug the serial cable from RS232_0 on the Olimex board to your computer Power cycle the board Now you ll want to send the program to the Olimex flash memory lpc21isp will write a flash block s worth of the program to RAM then burn that to flash To send the blinky hex file to the Olimex board run the following command lpc2lisp debug hex PHILIPSARM blinky hex dev ttyUSBO 38400 12000 See the Hello Blinky World section for an explanation of the command The program will write bits across the serial cable for a couple minutes Once the program is done you ll see Download Finished followed by a message that it s launching the new code Launching from the software doesn t work You ll need turn switch 1 off and push the reset button Then you should see both LED1 and LED2 glowing 6 6 Future Work The next step in software development is to write an eCos USB driver for the LPC2148 There are a few examples of other eCos USB dri
67. ponents oscillator etc o Arbitrary function generator o Oscilloscope Experiment o What we will do is apply a switching DC load at the SPS output and sweep its value The test circuit would be something like applying a square wave signal we could use an arbitrary function generator or an oscillator i e 555 timer to the gate of a NMOSFET with a series resistor and the drain of the FET connects to the SPS output through a series resistor There would also be a variable impedance in shunt with the FET which is comprised of a potentiometer with its two fixed terminals are connected to a voltage rail 5 V or something and its variable terminal is connected to the gate of another NUOSFET This will act as a variable impedance in shunt with a fixed load that is either saturated or cutoff This will introduce load changes in steps and we will then measure the voltage transients at the SPS output We will first pick values for C206 and R206 and sweep the load while observing the output Typical starting values for C206 and R206 are 1 nF and 0 ohms respectively and we decrement and increment those values respectively When we find that the ringing at the output is good enough i e a critically damped response at the output due to a step change in the load whatever values C206 and R206 end up with will be used NOTE Let us call this experiment A 7 1 3 4 Light Heavy load e Objectives o We will basically preform experiment A but the load change
68. r switch faster and to make sure that once the comparator is switching it completes the transistion Under normal SPS operation when U251 is keeping Q251 off the OUTPUT pin 1 of U251 is at zero volts thus the cap is acting like a low pass filter the node connected to pin 3 of U251 is the input to the filter If there are transients at the 3 3 V SPS output this node will also experience proportional transients If the magnitude of these transients are great enough but fast in duration then U251 s comparator switches which is undesirable so we want true ovevoltage events to trigger the comparator C251 will remove most of these false event transients When there is a true overvoltage event the comparator starts to switch If there is another transient false event where the magnitude of the voltage goes below the threshold the comparator could possibly try to switch back We want the comparator to avoid reacting to false transients C251 prevents this because as the comparator is rising its output voltage C251 raises the voltage on pin 3 of U251 thus reinforcing the comparator to keep on raising its output voltage This is positive feedback Also C251 decreases the rise time of the comparator Basically if there is something weird going on at the SPS output i e it is oscillating between 0 V and 3 3 V C251 will help to make sure that U251 turns Q251 off eventually turning off Q250 which will give a 150 ms time period for the weird things to go aw
69. rent etc However since there is a hierarchy of protection there will actually only be one effect maximum output current when the whole SPS is running Equipment o Various resistors and potentiometers o Oscilloscope o Current probe Experiment o With the whole SPS running nominally we want to apply a DC load to the output and decrease its value until something happens i e an inductor saturates U250 trips the output voltage rail oscillates etc This will be the effective maximum output current 7 1 6 2 Temperature rise Objectives o We expect that the U200 and the buck inductor will run the hottest So there will be a temperature gradient across the SPS Equipment o Various resistors and potentiometers o Oscilloscope o Current probe o Non contact thermometer i e Infrared thermometer Experiment o We will apply a varying load which will not cause any fault events to occur and notice the temperature gradient across the SPS and each block s and or component s incremental temperature change 7 1 6 3 Cleanliness of OV and CB trip points Objectives o When there is an overvoltage and overcurrent trigger event voltage current nodes around U250 and U251 will quickly change in value We want to observe what these transients look like and their effects on other nodes if any Equipment o Various resistors and potentiometers o Oscilloscope o Current probe o Voltage source o Hot air gun Experimen
70. ressor TVS this zener like diode protects the SPS specifically U200 in the event of an overvoltage at the input Specifications Calculations e It should have a breakdown voltage of about 20 V unlikely maximum bus voltage and a current carrying capacity greater than the fuse rated current It should have a fast response time and be unidirectional In the event of a sustained overvoltage at the input the only allowable part which can be destroyed is the fuse F200 That is what we want 5 1 2 Circuit Breaker Block 5 1 2 1 MAX5902 Circuit Breaker Resistor Network R250 R251 5 1 2 1 1 R250 Part Description e 61 9 kohm 0805 1 1 8 W Cut Tape ROHS Compliant Rohm MCR10EZHF6192 Digi Key p n RHM61 9KCCT ND 0 38 10 http www rohm com products databook r pdf mer10 pdf Purpose e R250 is part of the UVLO resistor divider of U250 Specifications Calculations e The UVLO voltage was specified to be 9 V See page 8 and Figure 3 in the MAX5902 datasheet Letting R251 10 0 kohm and using the typical value of Vonjoff 1 26 V the UVLO formula from page 8 in the datasheet is R250 R251 Vuvio Voniott 1 61 4 kohm The closet standard value was 61 9 kohm 5 1 2 1 2 R251 Part Description e 10 0 kohm 0805 1 1 8 W Cut Tape ROHS Compliant Rohm MCR10EZHF1002 Digi Key p n RHM10 0KCCT ND 0 38 10 http www rohm com products databook r pdf mcr10 pdf Purpose e R251 is part of the UVLO resi
71. roduction 2 Tools used 1 Serial Terminal 2 ISP Software 3 Cross Compiler 3 Serial Port Test 4 Hello Blinky World Example 1 Introduction License Issue Modifications From Original Source Code Review Compiling and Downloading Instructions 6 Results 5 eCos Port 1 Introduction 2 LPC2148 Port 3 Source Code Review 4 Compiling the eCos Demo 5 Downloading Instructions 6 Future Work 7 Construction and Test Plan 1 SPS ar oN Front end Circuit breaker CB Switcher Overvoltage OV Secondary supply 6 Final System block testing 2 ARM and Glue Circuitry 1 Reset Circuitry 2 Crystal Oscillator 3 USB interface 4 ARM Glue power up 5 ARM Glue final block testing 3 Software 1 Node Testing 2 Initial USB Testing 3 USB Performance Testing 4 Final System Testing 8 References 1 USB 2 Switching Buck Regulator 9 Appendix 1 User Manuals OF PO NS 2006 Capstone Project Final Report 1 Introduction Our Capstone project was sponsored by the Portland State Aerospace Society PSAS is a Portland State University student club that focuses on amateur rocketry projects Students and industry professionals design and build motors airframes avionics hardware and write software all with the end goal of launching an open source rocket All the designs and software are freely available on the PSAS website so any amateur group could duplicate our results Since the successful b
72. s 3 2 4 SPIs 1 2 2 I2C 1 2 2 16 bit timers 3 4 4 PWM channels 4 3 4 Watch dog reset Y Y Y brown out reset Y Y power on reset Y Y RTC Y Y N 3 2 3 2 Miscellaneous Warts Found 3 2 3 2 1 Atmel To use USB the system designer is forced to under clock the microcontroller at 48MHz It also doesn t have a real time clock only a real time timer The Atmel chip was discarded early in the selection process because of USB issues see below 3 2 3 2 2 Philips Philips was lacking in memory and the quoted SRAM size of 40KB is deceptive There is 32KB of SRAM for general use but 8KB of that is reserved for USB That puts it on the lower limits of our memory requirements The Philips part exclusively uses an internal 1 8V voltage regulator which means we can t hook up our switching power supply This increases the power consumption of the system Also the pin multiplexing may prove troublesome When PSAS designs a self correcting rocket all three PWMs will be used on a node to control motor servos The PWMs on the LPC2148 conflict with other devices we want to use such as SPI and UARTO However this need is far in the future and we may switch to a new microcontroller before then 3 2 3 2 3 STM The STM part also requires the microcontroller to be run at 48MHz to use USB Another wart was that the ADC conversion time is listed as 1ms This was unacceptable considering that the other two microcontrollers listed 2us conversion tim
73. s JTAG port Specifications Calculations 5 2 8 Power Good and Shutdown 5 2 8 1 Power Good Purpose e Input to microcontroller from SPS indicating status of incomming power Allows the microcontroller to perform evasive action should the power develop a problem Specifications Calculations 5 2 8 2 Power Shutdown Purpose e Output from microcontroller to the SPS to shutdown the SPS This will allow the SPS to be shut down under software control If the power comming to the node is still good the SPS will restart after a predetermined amount of time Specifications Calculations e Assure the default state of this output pin is such to allow the SPS to start before the microcontroller is up and running 5 2 9 Breakout of signals to application specific area Purpose e These are the golden resources we are providing to the future application specific functions of this board here we have access to all of the unused pins of the microcontroller and the debug port There are also unused pins on the debug port that are passed on to the group of connections to allow external eccess to the application specific area through the debug port Specifications Calculations 5 2 10 Status LEDs 5 2 10 1 Red LED D281 Part Description e LED High efficiency red with diffuse lens Package SOT 23 Digikey P N L71516CT ND http dkc3 digikey com PDEF T062 1848 pdf Purpose e To provide a user defined status indicator Con
74. s at the output Equipment o Oscilloscope o Current probe o Spectrum Analyzer maybe Experiment o This is simply powering up the SPS and observing the output and U251 s behavior 7 1 4 2 Check adequacy of comparator power supply e Objectives o Since U251 s power is derived from the 3 3 V SPS output which it also simultaneously monitors for overvoltages C250 is designed to keep power to U251 for 0 5 s given that the SPS output rail falls or other faults happen it should always keep U251 powered however the initial power up transients are important to observe Equipment o Oscilloscope o Current probe o Spectrum Analyzer maybe Experiment o This is simply powering up the SPS and observing the output and U251 s behavior 7 1 5 Secondary supply 7 1 5 1 Estimation of secondary supply voltage and maximum current e Objectives o The voltage regulation for this block will most likely be done by a low dropout LDO linear voltage regulator It was estimated that the node between L200a and L200b will switch between 1 6 V and 7 2 V but the actual value will be determined in experiment The voltage at the output of the secondary buck should be enough to be regulated down to 5V Equipment o Various resistors and potentiometers o Oscilloscope o Current probe o Spectrum Analyzer maybe Experiment o With the whole SPS running we will leave the secondary buck voltage regulator unloaded and measure the volta
75. s when subjected to surges or abnormal voltages therefore it should be placed behind the USB TVSS The circuit is effectively a Tee fiter with the shunting member connected to IO ground Interesting note The USB 2 0 spec on the bottom of page 142 states that the use of ferrite beads on a full speed USB device is discouraged pI oC SSS I OS Uy TARE er CTT Nese 40 Frequency Hz Image from Panasonic EXCCET data sheet Fig Glue 4 5 2 3 6 IO Power and Ground Purpose e The power and ground needed for this block are identified as O_3 3V and l O_Ground They are single point connections to the SPS 3 3V and ground made directly back at the supply to prevent ground loops and to reduce power disturbance with other node systems 5 2 4 Power on reset 5 2 4 1 Microcontroller Supervisory Circuit U283 Part Description e Supervisory Circuit Package SOT 23 3 Microchip MCP130T 315I TT Digikey P N MCP130T 315I TTCT ND http rocky digikey com WebLib Microchip Web 20Data MCP120 130 20Series pdf Purpose e Provide power on reset of sufficient time duration Assert reset to lock the processor if Vpp goes below level allowed by microcontroller Specifications Calculations e The LPC2148 has integral power up reset functionality that needs to be considered in conjunction with this part The LPC2148 User Manual section 3 10 describes the reset requirements and section 3 13 describes the brownout functionality If
76. s will be more drastic being almost no load to a heavy load Equipment o See experiment A Experiment o See experiment A 7 1 3 5 Hot Cold temperature e Objectives o We will basically preform experiment A but we will also sweep the temperature This makes sense as the rocket will experience not an extreme but a noticeable temperature gradient while it is on the ground during launch and flight Equipment o See experiment A o Hot plate or hot air gun o Freeze aerosol can Experiment o See experiment A 7 1 3 6 High Low input voltage e Objectives o We will basically preform experiment A but we will disconnect the U200 s input from the SPS and use a voltage source to sweep the input voltage The power bus voltage rail is specified to never be below 9 V or more than 20 V under normal operating conditions This affects U200 s efficiency as Vin is changing Equipment o See experiment A o Voltage supply Experiment o See experiment A 7 1 4 Overvoltage OV 7 1 4 1 Start up of OV no latch up no oscillations e Objectives o Upon initial power up meaning all caps and inductors have zero stored energy we want to make sure that as U200 s 3 3 V SPS output rail is being brought up U251 does not react to any overvoltage glitches at the output which will cause U250 to break the circuit This could be a problem in that the SPS may take a long time to stabilize because U251 continually responds to overvoltage
77. sappear after Q250 turns off within 150 ms then the normal start sequence is reinitiated Since the purpose of U250 was to be a circuit breaker we decided not to use the ON IOFF pin to turn Q250 off via any SPS feedback Only an UVLO condition would be a trigger event The UVLO threshold was specified as 9 V See R250 and R251 This meant that when a trigger event other than a UVLO condition happens U250 would turn Q250 off in 4 us and would reinitiate the start sequence after a trigger event free 150 ms time period We needed a way for the LPC2148 U280 microcontroller to turn off the SPS so we connected a logic level NMOSFET Q282 to a GPIO pin and connected the drain of Q282 to the ON OFF pin of U250 Also we connected the active low PGOOD pin to another GPIO pin for monitoring and or interrupt purposes See the GLUE Logic section regarding U280 and Q282 See R253 and Q251 for the overvoltage to overcurrent trigger event emulation One bad thing that we did not like was the relatively high supply current of U250 being 1 mA to 2 mA We believe that U250 will draw the most current from the power bus when the SPS is in a standby shutdown mode NOTE According to the MAX5902 datasheet there are two package options for the different versions of the MAX5902 a TDFN and SOT23 package All SOT23 packages have the specification that This device is constructed using a unique set of packaging techniques that impose a limit on the thermal profile the
78. sient Response http www linear com pc downloadDocument do navid HO C1 C1003 C1042 01143 C1083 P1735 D4165 e National Semiconductor Application Note 1197 Selecting Inductors for Buck Converters http www national com an AN AN 1197 pdf page 1 e Engineering Notes for Recovery Node Component Design for LV2 Power Electronics Except Main Battery http psas pdx edu RecoveryNodeLV2 action AttachFile amp do get amp target ComponentDesign pdf 9 Appendix 9 1 User Manuals e Philips LPC2148 ARM7 microcontroller User manual http www semiconductors philips com acrobat_download datasheets LPC2141 42 44 46 48 1 pdf e Olimex evaluation board http www olimex com dev lpc p2148 html
79. stor divider of U250 Specifications Calculations e R251 was specified to be 10 0 kohm See page 8 and Figure 3 in the MAX5902 datasheet 5 1 2 2 Overcurrent Circuit Breaker Protection U250 Part Description e MAX5902AAETT 72 V SOT 23 Simple Swapper How Swap Controller Ordered samples from vendor no Digi Key http pdfserv maxim ic com en ds MAX5902 MAX5903 pdf Purpose e This hot swap controller IC serves two purposes 1 circuit breaker and 2 the first stage of UVLO protection The version we chose had a input voltage range of 9 V to 72 V a 300 mV circuit breaker threshold voltage limited inrush current soft start and was an automatic retry circuit breaker It also had a built in thermal shutdown and active low power good PGOOD indicator output pin The device needed a UVLO resistor divider network R250 R251 and an external PMOSFET Q250 switch There are four events which will cause Q250 to turn off 1 if there is undervoltage at the input 2 if there is overcurrent 3 if the die temperature exceeds 125 C and 4 the ON IOFF pin 6 is forced low for at least 10 ms See the MAX5902 datasheet Specifications Calculations e The reasons we chose the 300 mV automatic retry circuit breaker version was that we wanted the SPS to be able to recover from a fault condition by itself and we expect that the nominal load current will not be very close to the 400 mA maximum limit but closer to 300 mA or less Henc
80. t o We will disconnect the power bus and apply a voltage source at the SPS input disconnect the gate of U282 from U280 and connect a voltage source to the gate vary the load at the SPS output and use a hot air gun which we can use to cause any one of the four trigger events 7 1 6 4 Voltage s seen when coming out of undervoltage UV lockouts both CB and the switcher Objectives o Only U250 and U200 have UVLO lockout functionality We want to observe what transients occur when there is an undervoltage event when the two IC s go into lockout and when the input voltages are brought back up to get the IC s out of lockout specifically at U250 U200 and the SPS output Equipment o Oscilloscope o Voltage source o Arbitrary function generator maybe Experiment o We will disconnect the power bus from the SPS and replace it with a voltage source to vary the input voltage to cause the two IC s to enter lockout stay in lockout for some time and bring them back out of lockout We may even use an arbitrary function generator to quickly ramp step the input voltage to see how the IC s will respond 7 1 6 5 Efficiency e Objectives o The specified efficiency of the SPS was to be gt 70 at a load current of 400 mA We will connect a constant source at that load to measure the specified efficiency Equipment o Oscilloscope o Current probe Experiment o The efficiency x of a switching voltage regulator is x Pioag Prot
81. t sends data over the serial port In Linux minicom is the software of choice Minicom comes preinstalled with Debian Linux and open source under the GNU General Public License GPL used version 2 1 compiled Nov 4 2005 6 2 2 ISP Software To download programs into flash and RAM on the LPC2148 a programmer needs to have In System Programming ISP software This software uses the ISP command specification to send program binaries over the serial port or JTAG Typically this means writing a chunk of program to RAM and then burning it to flash A programmer would have to type hundreds of commands over the serial port if they wanted to do this manually There are several options for ISP software Philips gives away a flash utility for LPC2xxx chips However they only distribute the executable which doesn t work under Linux http www semiconductors philips com products microcontrollers support software_download lpc2000 index htm Macraigor systems also distributes a flash memory programmer It works under Linux and Windows but requires JTAG A JTAG connector is fairly expensive so we wanted another alternative http www macraigor com flash_prog htm The ISP software selected for use is a flash programmer that uses the serial port It runs under Linux and in Windows using Cygwin and is fully open source http guest engelschall com martin lpc21xx isp used version 1 31 The program is one c file that you ll need to compile Yo
82. tain the frame number and endpoint number that transmitted the data If each packet contains a unique incremental packet ID the host side can check that the endpoints are sending correct data every frame and look for dropped packets The isochronous code will be fairly complicated An eCos USB driver is not strictly necessary for this test but would be helpful An eCos USB driver would handle the USB initialization and would allow the designer of the isochronous test code to focus on the test code However this requires adding isochronous transfer support to eCos a task that may take several months 7 4 Final System Testing e System specifications o Max application specific current consumption o Max MIPS o Time to first instruction power up sequence and times o OV CB and brownout reset to first instruction sequence and time e Environmental testing o Vibration o Temperature o Pressure 8 References 8 1 USB e USB org documentation on USB standards http www usb org developers docs e USB in a Nutshell an introduction to USB http www beyondlogic org e USB 2 0 standard http www usb org developers docs usb_ 20 zip 8 2 Switching Buck Regulator e Linear Technology Application Note 19 LT1070 Design Manual http www linear com pc downloadDocument do navid H0 C1 C1003 C1042 C1031 C1061 P1266 D4176 e Linear Technology Application Note 76 OPTI LOOP Architecture Reduces Output Capacitance and Improves Tran
83. tal having a C of 20 pF The table specifies Cy to be 38 pF The closest standard value to this is 39 pF 5 2 5 2 2 C282 Part Description e 33 pF 50V Ceramic chip NPO 0805 Panasonic ECJ 2VC1H330u Digikey P N PCC330CGCT ND http www panasonic com industrial components pdf abj0000ce1 pdf Purpose e Oscillator load capacitor Cyx2 Influences oscillator frequency by being part of the resonant feed forward impedance Specifications Calculations e Specified by Phillips in users manual table 280 on page 286 When choosing a crystal having a C of 20 pF The table specifies Cy to be 38 pF However this capacitor is in parallel with the load capacitance of the CD4024 ripple counter The nominal load capacitance on all digital inputs of the CD4024 is 5 pF Cl 38 pF 38 pF 33pF 5 pF 33 pF is a standard value Having the nominal capacitance of Cx and Cx being slightly unequal provides an increased energy efficiency in the oscillator according to Tim 5 2 5 3 Binary ripple counter U281 e The 12 MHz clock needs to be divided by 8 to form the 1 5 MHz SPS sync signal After our research even today the smallest package with the most direct approach to providing this divide function is a cascaded series of D flip flops One would think there were a better way Part Description e CD4024 7 stage CMOS ripple counter 14 TSSOP package TI CD4024BPWR Digikey P N 296 12760 1 ND http focus ti com lit ds symlink
84. teady state nominal forward current through CR250 lt 1 mA See C250 5 1 3 6 TLV3012AIDBVT Secondary Power Supply Cap C250 Part Description 2 7 uF 10 V 0805 X5R Cut Tape ROHS Compliant Kemet CO805C275K8PACTU Digi Key p n 399 3127 1 ND 7 02 10 http www kemet com kemet web homepage kechome nsf vapubfiles F3102X5R pdt file F3102X5R pdf Purpose Along with CR250 C250 forms the power supply for U251 C250 is charged to a voltage less a forward diode drop see CR250 from the 3 3 V SPS output rail under normal operating conditions U251 draws a constant 2 8 uA supply current so CR250 is always trickle charging C250 therefore the voltage across C250 will be Vfcreso 0 37 V this is worst case Vf less than 3 3 V See CR250 However U251 can operate from 1 8 V to 5 0 V Since the voltage at V of U251 is approximately 3 0 V and the lower limit of the supply voltage range of U251 is 1 8 V C250 has to be able to store enough charge such that if the SPS output drops down by a certain amount of voltage U251 is still powered for a certain amount of time thus preventing U251 from power cycling if the SPS output ramps back up to 3 3 V We want to prevent this because as U251 is powering up the comparator could possibly switch That behavior has to be observed in experiment but we assume that the initial state of the comparator will be logic low If the SPS output toggles or drops in value we want U251 to have power for a spec
85. ted a switcher which had an internal switching frequency of at least 1 MHz low switch resistance could supply at least 1 A of current had a shutdown or disable pin could be synchronized with an external clock and was in a small package We borrowed U200 from the previous LV2 SPS design because for the given PSAS specs it was the best fit There is no direct output undervoltage protection within the SPS however if the voltage at the output starts to fall due to an increasing load the circuit breaker protection will kick in See U250 There is a microcontroller supervisory circuit U283 in the GLUE logic section which will reset U280 if the 3 3 V rail drops below a certain threshold voltage 3 075 V version for a specified amount of time However U283 cannot correct the fault condition but only keeps U280 reset given that the SPS output rail is still below the threshold voltage Other than an overcurrent event at the output the quality of regulation by the SPS specifically U200 will dictate if the SPS output rail drops See the GLUE Logic section for clock synchronization with X281 and U281 and U200 s SYNC pin pin 8 5 1 4 2 LT1767EMS8 UVLO Lockout Resistor Network R209 R210 5 1 4 2 1 R209 Part Description 60 4 kohm 0805 1 1 8 W Cut Tape ROHS Compliant Rohm MCR10EZHF6042 Digi Key p n RHM60 4KCCT ND 0 38 10 http www rohm com products databook r pdf mcr10 pdf Purpose e R209 is part of the UVLO resistor div
86. th of the oscillator The oscillator can operate anywhere between 1 and 30 MHz when using this internal amplifier Specifications Calculations e We want the system clock oscillator to produce a frequency that is simultaneously a factor of the highest CPU clock frequency possible which is 60 MHz a factor of 48 MHz for the USB clock and a factor of a frequency somewhere around 1 1 to 1 5 MHz for the SPS synchronization A 12 MHz system clock meets this need For USB clock 12 MHz 4 48 MHz Hore CPuUschock L25 MHze eo i iG OME z For SPS Syne I2 Miz y 6 1 5 UE e Specifications required by Phillips in the users manual table 7 on page 19 Philips provides three posible C values The one closest to the Citizen CS10 is 20 pF Philips requires for 10 to 15 MHz range Citizen crystal provides C crystal load capacitance 20 pF 18 pF Rg max series resistance lt 220 ohm 50 ohm Frequency tolerance 50 ppm Footprint 6 0 mm x 3 3 mm 5 2 5 2 Oscillator load capacitors C281 C282 5 2 5 2 1 C281 Part Description e 39 pF 50V Ceramic chip NPO 0805 Panasonic ECJ 2VC1H390u Digikey P N PCC390CGCT ND http www panasonic com industrial components pdf abjO000ce1 pdf Purpose e Oscillator load capacitor Cx Influences oscillator frequency by being part of the resonant feed forward impedance Specifications Calculations e Specified by Phillips in users manual table 280 on page 286 When choosing a crys
87. the formula to solve for the buck output inductor it equated to about 1 4 uH We would want to use that value of inductance if we needed to supply higher output currents as the smaller inductor would have a higher saturation current lower DC power losses but larger core losses The biggest concern however in not using the smaller inductor was staying away from discontinuous mode operation We did not want to do this so we ignored the dependence of C200 to L200a b as is shown by the formula and found L200a b as wee did See L200a L200b Using the formula again with the 100 uH 94 uH inductor and solving for Vpp we got Vpp 74 uV which is negligible Under nominal operating conditions we expect a flat 3 3 V output 5 1 4 11 LT1767 FB Resistor Network R200 R201 5 1 4 11 1 R200 Part Description e 10 0 kohm 0805 1 1 8 W Cut Tape ROHS Compliant Rohm MCR10EZHF1002 Digi Key p n RHM10 0KCCT ND 0 38 10 http www rohm com products databook r pdf mcr10 pdf Purpose e This along with R201 forms the feedback FB resistor network which sets the value of Vout of U200 Specifications Calculations e The LT1767 datasheet on page 7 suggested R200 to be 10 kohm 5 1 4 11 2 R201 Part Description e 17 4 kohm 0805 1 1 8 W Cut Tape ROHS Compliant Rohm MCR10EZHF1 742 Digi Key p n RHM17 4KCCT ND 0 38 10 http www rohm com products databook r pdf mer10 pdf Purpose e This along with R200 forms the feedback
88. the optimal eye pattern of data rise fall times Specifications Calculations e 7 1 6 1 states this capacitance is to be less than 75 pF and is to be placed between Rg and the tranceiver See page 142 of the USB 2 0 specification 5 2 3 3 USB Full Speed Select R291 Part Description e 1 5k ohm resistor 1 8 watt Chip 1 Thick film 0805 package Panasonic ERJ 6ENF1501V Digikey P N P1 50KCCT ND http www panasonic com industrial components pdf AOA0000CE2 pdf Purpose e USB Full Speed Select pull up resistor Rey required by USP 2 0 electrical specification to select Full Speed Specifications Calculations e This 1 5 K ohm resistor called Rey is to pull up the D signal to 3 3 volt IO power source to indicate Full Speed mode prior to enumeration It is described in chapter 7 under signaling on page 121 of the USB 2 0 specification 5 2 3 4 USB Port Transient Suppressor U282 Part Description e USB port transient suppressor Package SOT 23 6 TI SN65220DBVR Digikey P N 296 9694 1 ND http focus ti com lit ds symlink sn65220 pdf Purpose e To provide transient voltage suppression that may be picked up on the external USB bus Specifications Calculations e This component provides 15 kV of ESD capability to the D and D USB signals The part adds 35 pF of capacitance on each signal circuit to ground This values is still within the USB 2 0 edge capacitance spec of 75 pF Figure Glue 2 illustrates the parts intern
89. through U250 under certain events Also the unlikely maximum bus voltage is 20 V which we should never see but which is worst case With Id avg 835 mA we want CR200 to be rated at a higher forward current Also the reverse voltage needs to be greater than 20 V and the forward voltage needs to be low We chose a part with If 1 5 A Vr 30 V and Vf lt 0 37 V The forward current If spec is a little overkill but since it is in a small 2 pin package we like it Since this is a high frequency node CR200 and C201 will be closely grounded together 5 1 4 9 Split Buck Inductor L200a L200b Part Description e D3118 470 R Low Profile Power Inductor 47 uH Shielded Drum Package Bobbin ROHS Compliant Tape and Reel http www cooperet com library products PM 4129 20SD3118 20Series pdf Purpose e This is the main buck output inductor L200a and L200b are one inductor but are split such that we can have a secondary output voltage supply of 5 V see CR251 and C252 We chose the shielded drum or bobbin style of package because they are smaller than similar torroid packages Specifications Calculations e Fora worst case scenario we expect to run the inductor s at an ambient temperature of 80 degrees C That is the SPS is off and the inductors are not dissipating any power We also want the inductor s saturation current to be larger than 400 mA and be big enough both in value and physical size such that they will not easily go in
90. tion between the analog ground bus and the SPS ground USB filtering block e This block provides EMI and RF suppression from noize that might be picked up from the external USB bus There is also 10 kV of surge suppression current limiting power decoupling and a single point connection between IO ground and the SPS ground Finally this block provides the 1 5 k ohm pullup to indicate this endpoint is to use USB full speed Power on reset e This block provides the reset signal required by the microcontroller The reset is released after the SPS has come up to the proper operating voltage and after the time required by the microcontroller to assure it is running properly Oscillator and divider e This block provides the 12 0 MHz for the microcontroller system clock Part of this block is contained within the microcontroller This block also divides down the 12 0 MHZ by 8 to create a 1 5 MHz clock to syncronize the SPS This SPS syncronization assures that switching noize created by the SPS remains constant and at a known frequency allowing it to be more easily filtered out should it cause problems with any of the circuits later down the road RTC crystal oscillator e This block provides the 32 768 kHz clock signal used by the microcontrollers real time clock This block also contains the clock power to maintain the time of day clock when the node power is off Debug port e This is an external connector providing standard JTAG Joint Test
91. to discontinuous mode or burn up due to power heat dissipation From page 2 in the SD3118 470 R datasheet with a 40 degree C rise in temperature i e running at 120 degree C the total power loss due to the inductor is 200 mW Summing the non linear core losses and DC power losses should be less than this total power loss We went through a trial and error process of finding the inductor value given that the saturation current should be greater than 400 mA and the range of current that the inductor will carry is about 10 mA to 300 mA We specified the average DC current being equal to 300 mA After using the formulas and graphs in the SD3118 470 R datasheet we found that we wanted an inductor of approximately 100 uH Since the inductor is split we had to use two 47 uH inductors Given f 1 5 MHz L200a 47 uH Vin 20 V Vout 3 3 V Idc 300 mA Vd 0 37 V see CR200 datasheet and Vsw Rsw Idc 66 mV see U200 datasheet for Rsw and K 12 and DCR 1 21 ohm taken from the SD3118 470 R datasheet From the table on page 1 in SD3118 470 R datasheet the peak to peak magnetic field is given by the formula in note 4 Bp p K L200a delta_l where K is taken from the table Bp p and L200a are already in units of mT and uH respectively To find the ripple inductor current delta_l we calculate the applied volts microseconds across L200a b and find delta_ from the inductor current differential equation V L200a di dt The applied volts
92. trolled by microcontroller Specifications Calculations e Connected to general purpose output pin P1 17 Called Status 2 Ve at I 2 1V 20 mA 5 2 10 2 Green LED D282 Part Description e LED Green with clear lens Package SOT 23 Digikey P N L71508CT ND http dkc3 digikey com PDF T062 1848 pdf Purpose e To provide a user defined status indicator Controlled by microcontroller Specifications Calculations Connected to general purpose output pin P1 16 Called Status 1 Ve at I 2 1V 20 mA 5 2 10 3 Current limit resistors R289 R290 5 2 10 3 1 R289 5 2 10 3 2 R290 Part Description e 604 ohm resistor Chip 1 Thick film 1 8 watt Package 0805 Panasonic ERJ 6ENF6040V Digikey P N P604CCT ND http www panasonic com industrial components pdf AOA0000CE2 pdf Purpose e LED current limit resistor Specifications Calculations e V 2 1 V We specified the LED drive current to be 2 mA SOW 2 IN ay 1 2V 2 mA 600 ohm Closest standard value is 604 ohm 5 2 11 Test points 5 2 11 1 SPS Off 5 2 11 2 Pwr Good 5 2 11 3 1 5 MHz SPS Sync Purpose e To gain access to signals during testing Specifications Calculations e These are just small scrape pads on the PCB to touch a test probe onto 5 2 12 Configuration trace cuts or solder jumpers Analog Vrer RTC Power Vegart Purpose e To allow alternate configuration of these supply vlotages Specifications Calculations e The d
93. ttp www semicon panasonic co jp ds eng SKH00017BED pdf Purpose e CR250 and C250 form U251 s power supply This diode prevents C250 from discharging anywhere but to the V supply pin of U251 U251 is indirectly powered by the 3 3 V SPS rail Pin 6 V of U251 will be charged to a value very close to the 3 3 V SPS rail As U251 draws more current when needed and its V voltage drops CR250 s Vf below the SPS voltage CR250 will re charge C250 Therefore the average DC current through CR250 is not easily calculable but will be on the order of tens to hundreds of uA Schottky diodes were chosen for their fast switching and reverse recovery times In response to a overvoltage event at the 3 3 V SPS output U251 will output a logic high and turn Q251 on which will cause an overcurrent event at U250 which will in response turn Q250 off thus circuit breaking the bus rail from the SPS and the 3 3 V SPS output voltage rail will go to zero That is the sequence of events without delay times This is the way U251 emulates an overcurrent event from an overvoltage event Specifications Calculations e CR250 has a low forward voltage and U251 has an input voltage supply range of 1 8 V to 5 0 V so when the SPS voltage is being brought up C250 is being charged through CR250 leaving the voltage of SPS minus the Vf of CR250 at pin 6 V of U251 V 3 3 V 0 05 V 3 25 V approximately See the first graph on page 2 of the MA2Q705 datasheet given that the s
94. u should add the directory containing the compiled program to your path 6 2 3 Cross Compiler In order to compile programs for the ARM chip you need a cross compiler A cross compiler builds native code ARM programs on non native systems Intel x86 GNU provides a c and c compiler tool chain called gcc To build a gcc cross compiler follow the instructions at http psas pdx edu DebianCrossCompilerHowto Replace any mention of powerpc or ppc with arm used gcc 4 0 to build the cross compiler 6 2 3 1 eCos The real time operating system RTOS chosen to run on the nodes is the embedded Configurable operating system eCos 6 2 3 2 Building eCos 1 Goto http ecos sourceware org getstart htm and follow the instructions under the section eCos Do not follow the Toolchain instructions those are equivalent to making the cross compiler don t suggest installing eCos in opt ecos because it requires root to run the eCos configuration tool and update your sources 2 Make sure to add the configtool path to your PATH environment variable configtool is found in SECOS_INSTALL_DIR ecos ecos 2 0 tools bin 3 Go to hitp ecos sourceware org anoncvs htm and follow the instructions for checking out the latest eCos repository Make sure that your environment has Ecos_REPosttory set to the packages directory in the eCos CVS sources Run configtool Choose Build gt Repository and enter the path to the eCos CVS dir
95. udo apt get install eagle 4 1 1 3 Getting the Eagle schematic files for this project The schematic files for this project are kept in the PSAS Subversion source repository The following Linux command checks out the CAD sub tree from the repository which includes the node 4 files and needed libraries To find out more about Subversion see lt http subversion tigris org gt svn co http svn psas pdx edu svn psas trunk cad The above command will check out the entire PSAS cad directory The files you will actually need for this project are e libraries psas eagle library lbr This is the standard PSAS parts library e lv2 node4 frontend node4 frontend sch This is the schematic od the project as seen above e lv2 node4 frontend node4 frontend brd This is the board layout e lv2 node4 frontend node4 lbr This is a library of special parts used in this design It is intended that eventually the lt node4 lbr gt library be merged into the lt psas eagle library lbr gt library at a future time 4 1 1 4 Maintaining the files To maintain the schematics be sure you have latest copies before starting by doing an update command Once your changes are made check them into the repository using the check in command svn up get latest update Sw Si check in your latest work 4 2 Board Layout This is the preliminary board layout it is not complete The board dimensions are 2 in x 3 in with traces on only two sides Components ar
96. ut finally disastrous launch of Launch Vehicle No 2 LV2 the PSAS Avionics Team has been redesigning the avionics system This new system called the LV2b avionics system should avoid the limitations of the old system e Replace the Microchip PIC processors which require Windows based development tools and a proprietary commercial compiler with a more open source microcontroller e Use saner communication protocols either a more easy to use CAN system of IDs or possibly switch to USB The goal of the PSAS Capstone team is to design the generic front end that interfaces between all the nodes of the system GPS IMU recovery system etc and the communication bus 2 Final Requirements There are three requirements for completion of our capstone project e anEAGLE schematic for the generic node front end e the EAGLE board layout started and e a VERY detailed engineering notebook going over each part of the design These engineering notebooks should cover the three major areas of design the Switching Power Supply SPS the microcontroller and glue circuitry and the software The notebooks should contain a detailed discussion of how the design works and an explanation of all component choices and values A smart experienced engineer should be able to use this document to understand why the design is the way it is 3 System Level Design 3 1 Communications Bus Part of our capstone project was to decide what communications
97. validation logic section is not needed or would be superflous since each USB endpoint communicates directly with a USB hub which essentially provides the function of isolating errant nodes from disrupting the entire bus Finally the function of electrical transient suppression is provided by this USB filtering block The following figure illustrates the USB filtering block IO Power connection Fig Glue 1 5 2 3 1 Driver impedance matching resistors R281 R282 Part Description 33 2 ohm resisior 1 8 watt Chip 1 Thick film 0805 package Panasonic ERJ 6ENF33R2V Digikey P N P33 2CCT ND http www panasonic com industrial components pdt AOA0000CE2 pdf Purpose e Intrinsic driver impedance Rs required by USP 2 0 electrical specification Specifications Calculations e The intrinsic driver impedance Rs is described in chapter 7 1 1 3 of the USB 2 0 specification under High Speed Driver Characteristics on page 129 Rs is 1 2 of the total bus impedance of 90 ohms or 45 ohms This total value is to include the contributions of cabling and connectors and therefor should be less than 45 ohms See Figure 7 3 in the USB 2 0 spec 5 2 3 2 Edge rate control capacitor C289 C290 Part Description e 18 pF 50 volt Chip NPO 0805 package Panasonic ECJ 2VB1H103K Digikey P N PCC103BNCT ND http www panasonic com industrial components pdf abj0000ce1 pdf Purpose e Edge rate control capacitor Cedge intended to obtain
98. vents chip switching transient from going onto power rail Also a source of very short duration energy to supply the switching transient locally Specifications Calculations e Typical logic guidelines use 10 to 100 nF 5 2 3 USB filtering block e The USB bus is a potential source of harmful external noize that can be coupled onto the node with adverse effects This noize can come in several forms RF signal noize transient switching noize and harmful fault currents on the bus This block addresses these three forms of noize The previous node design used a CAN bus and a Physical Layer PHY chip to isolate the electrical connection between the CAN bus and the microcontroller used at that time The PHY converted the single ended uni directional TTL signals from the microcontroller into the differential bi directional signal pair needed by the CAN bus This PHY also provided electrical transient suppression and bus protocol validity logic that prevented and errant microcontroller from disrupting the entire CAN bus for the other bus peers This is mentioned here because this level of functionality is still desired however the situation is totally different in the following ways It should be stated PHY chips for USB similar to the one previously used for CAN exist however are inappropriate for this design Particularly the LPC2148 is actually providing the needed differential bi directional electrical interface needed by USB A protocol
99. ver that meets most of our needs there will probably be some custom hacking on it 3 1 2 3 Summary Hardware Requirements Requirement CAN USB best bus EMI immunity Differential bus Differential bus tolerance to over voltage built in none CAN safety critical systems usage automobiles some medical devices CAN message priority individual node priority bandwidth priority bus topology peer to peer host initiated speed 1Mbps 12Mbps full speed USB Software Requirements Requirement CAN USB best bus packet retransmission automatic depends on message type USB packet size up to 8 bytes up to 1023 bytes USB connectivity special connection disrupts debugging plugs in directly to a laptop USB previous open source drivers very few good Linux support USB As the chart shows the Avionics team wanted the CAN bus because it provided better hardware reliability and was widely used in safety critical systems However USB was an overall win for the Software team In the end the promise of higher bandwidth and better open source support won over the Avionics team 3 2 Microcontroller 3 2 1 Requirements The microcontroller for the node front end must meet the following requirements 3 2 1 1 3 2 1 3 3 2 1 4 3 2 1 5 3 2 1 6 3 2 1 7 Architecture Must be gt 32 bits Should have many implementations by more than one manufacturer if possible Should have decent integer math ALU e g 32 x 32 gt
100. vers in the eCos repository but they only use control and bulk transfers Implementing eCos isochronous transfer support will require intensive development and extensive knowledge of eCos and USB Once the eCos USB driver has been implemented a user land Linux USB driver needs to be developed for the flight computer This project will require both Linux and USB knowledge Both projects are beyond the scope of this capstone project 7 Construction and Test Plan 7 1 SPS 7 1 1 Front end 7 1 1 1 Turn on transient for passives e Objectives o We want to observe the transient response of the Front end Passive Block as the voltage is applied to its input and possibly having its own transients Equipment o Arbitrary function generator o Various resistors and potentiometers o Oscilloscope o Spectrum Analyzer maybe Experiment o We will disconnect the Front end Passive Block from the rest of the SPS and apply a DC load at its output and apply a ramping voltage source at the input simulating the power bus We will step the voltage in varying times and magnitudes 7 1 2 Circuit breaker CB 7 1 2 1 CB trip point make sure fuse doesn t blow e Objectives o We want to observe that the fuse F200 does not blow given an overcurrent condition and the Circuit Breaker Block is in the process of tripping The design specifies that the fuse should never blow before the circuit breaker does given all components are operating correctly
101. w panasonic com industrial components pdf abj0000ce1 pdf Purpose e Oscillator load capacitors Cx1 and Cx2 Influences oscillator frequency by being part of the resonant feed forward impedance Specifications Calculations e Specified by Phillips in users manual table 280 on page 286 5 2 6 2 Frequency control crystal X282 Part Description e 32 768 kHz Surface Mount Crystal Tuning Fork CM415 package 4 1 mm x 1 5 mm Citizen CM415 32 768KDZFTR Digikey P N 300 8193 1 ND http dkc3 digikey com PDF T062 0942 pdf Purpose e The real time clock is driven by an internal oscillator using an external crystal for frequency reference This crystal is the primary frequency determining component of the real time clock oscillator The resonant circuit formed by this crystal and the two load capacitors is in the feed forward path of the oscillator The oscillator is intended to operate at 32 768 kHz which is 2 Specifications Calculations e Specifications required by Phillips are in the users manual table 280 on page 286 Philips requires Citizen crystal provides C crystal load capacitance 13 pF 12 5 pF Rg max series resistance lt 100k ohm 70 k ohm Frequency tolerance 20 ppm Footprint 4 1 mm x 1 5 mm 5 2 6 3 Power to oscillator e The RTC has a seperate power source on pin 49 VBAT This can be connected to an external 3 2 volt battery or the SPS 3 3 V supply 5 2 7 Debug port 5 2 7 1 Connector
102. wer loss and non linear core losses sum to 109 mW 11 mW 120 mW lt 200 mW so this inductor should work 5 1 4 10 Buck Output Cap C200 Part Description e 22 uF 6 3 V 0805 X5R Cut Tape ROHS Compliant Panasonic ECG ECJ 2FB0J226M Digi Key p n PCC2401CT ND 8 31 10 http dkc3 digikey com PDF T062 1235 pdf Purpose e This is the buck output switching regulator capacitor To maintain more precise regulation the capacitance should be constant as much as possible therefore a X5R X7R or NPO temperature coefficient cap should be used Specifications Calculations e Since this is the buck output cap and there is overvoltage protection at the output see U251 it only needs a voltage rating a little greater than 3 3 V We found a 6 3 V rated part We would prefer to have a smaller cap than say C203 so a ceramic part was used Using the formula on page 23 in the Linear Technology Application Note AP 19 C200 1 8 L200a L200b f 2 Vpp Vout 1 Vout Vin where L200a L200b is the 100 uH 47 UH 2 94 uH buck output inductor Vout 3 3 V Vin 20 V f 1 5 MHz Vpp is the output voltage ripple and the ESR term is dropped In contrast to C201 the output voltage ripple is significant because we want an ideal 3 3 V DC output voltage The maximum output voltage ripple was specified to be Vpp 5 mV The previous LV2 SPS design used a 22 uF buck output cap and we wanted to use the same value Using
103. y allowable and designed for component that should ever be destroyed in a fault event is the fuse This block also is the first stage in under voltage lockout UVLO protection If the voltage on the power bus is below 9 V this block will disconnect the rest of the SPS from the power bus Overvoltage Protection Block e This block protects the SPS from overvoltage at the SPS out meaning if the 3 3 V SPS rail tries to increase past a certain threshold this block will engage the circuit breaker block which will disconnect the rest of the SPS from the power bus It is powered by the SPS output itself but has the ability to be powered for a finite amount of time 0 5 s while the SPS rail is zero volts Switcher e This is the switching voltage regulator block It specifically is a buck topology This block regulates the power bus voltage its input is slightly less than the power bus voltage to the specified 3 3 V SPS voltage 3 3 V SPS e This is the output of the SPS which powers all 3 3 V parts on the nodes It is specified as a 3 3 V 400 mA max power supply Power LED e This block only indicates if the 3 3 V SPS rail is up It lights an LED to signify this The LED is on as long as the SPS is on This block is only useful when a user is trouble shooting the SPS opened LV2b rocket on the ground Secondary Voltage Supply e This block acts as a secondary buck supply where it taps the buck output inductor in the Switcher blo

PSAS Avionics Node Front End for LV2b Rocket To

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