MIC2873_EB1.13 MB
Contents
1. MICREL General Description The MIC2873 is a high current high efficiency flash LED driver which can operate in either torch or flash mode The MIC2873 has a built in internally compensated current mode PWM 2MHz boost converter which allows for the use of a very small inductor and output capacitor for stepping up the supply voltage to a high enough value at the OUT pin to drive the LED current If the supply voltage is high enough the synchronous switch of the converter is then fully turned on and the LED driver operates in linear mode MIC2873 also features a configurable safety timer which automatically shuts down the LED current after the safety timer duration is expired if the programmed LED current exceeds a certain current threshold These features make the MIC2873 an ideal solution for high resolution camera phone LED flashlight driver applications The MIC2873 can be controlled through the single wire serial interface and or external control pins A robust single wire serial interface allows simple control by the host processor to support typical camera functions such as auto focus white balance and image capture Datasheets and support documentation are available on Micrel s web site at www micrel com Requirements The MIC2873 evaluation board requires a bench input power source that is adjustable from 2 7V to 5 5V and is able to deliver greater than 4 5A at 2 7V Precautions The evaluation board does not h2. 10 Read Ony OOOO Duration 1250 00ms Thresh 250mA Low Battery Threshold 3ov MIC2873 Evaluation Board Revision 1 0 Micrel Inc MIC2873 Evaluation Board Evaluation Board Schematic L1 1H PVIN O 7 OUT C1 D2 JP3 JP2 4 7uF 10V gt a J2 m AGND p PGND O T OPTION FEN DC S7 LOND jj J9 o J4 M ist ap MIC2873YCS js T FEN O J3 AGND L JP1 NCI 4 DC 3 GND 1 TO USB TO SINGLE WIRE DONGLE Bill of Materials C1 C2 C1608X5R1A475K080AC Capacitor 4 7 uF 10V 10 X5R 0603 ES High Power Flash LED 4 1mm x 3 9mm x 2 1mm 220lux f f RE LUXEON Flash 6 Module 4mm x 4mm x 2 2mm LXCL MNO06 3002 Philips 180lux liep 1A m SML LXL99UWC TR 5 LED SQ 5W COOL WHT 6000K SMD 190Im 2ER103CW06000002 Edison a LED EES COOL WAT S00 swD e m COOL WHT 6000K SMD 2101m L1 PIFE25201B 1ROMS 39 Inductor 1 0pH 3 55A 2 5mm x 2 0mm x 1 2mm 1 2A High Brightness Flash LED Driver with Single Wire Notes TDK www tdk com Samsung www samsung com Philips www philipslumileds com Lumex www lumex com Edison Opto www edison opto com Cyntec www cyntec com Micrel Inc www micrel com ee od a a oa August 25 2014 11 Revision 1 0 Micrel Inc MIC2873 Evaluation Board PCB Layout Recommendations 45 mm J Eeen Cd Top Layer 45 Cmm Bottom Layer August 25 2014 12 Revision 1 0 Micrel Inc MIC2873 Evaluation Board MICREL INC 2180 FORTUNE DRIVE SAN
3. Shutdown and Idle Timing Waveforms Communication Details The serial interface requires delimiters to indicate the start of frame data as a series of pulses and end of frame indicated by a lack of activity for longer than Tiar The start of frame is the first high to low transition of DC when in idle mode The first rising edge resets the internal data counter to 0 p 1COUNT a paar t Ton p gt l Teat a ToToT AUTOMATIC LATCH A AFTER Tar EXPIRES START Figure 3 Data Word Pulse Timing A pulse is delimited by the signal first going below V and then above V within the latch timeout Tiar During this transition minimum on Ton and off Torr periods are observed to improve tolerance to glitches Each rising edge increments the internal data register Data is automatically latched into internal shadow address or data registers after an inactivity period of DC remaining high for longer than T ar To send register write commands the address and data are entered in series as two data words using the above pattern with the second word starting after the first latch period has expired After the second word is entered the IDLE command should be issued by leaving the DC pin high for 2Tenp to indicate the stop sequence of the address data words frame Revision 1 0 Micrel Inc After receiving the stop sequence the internal registers decode and update cycle is started with the shadow register v
4. evaluation board with the GND pin of the dongle as shown in Figure 5 the MICUSB Dongle should be faced down On the MIC2873 evaluation board the GND pin is the first pin of the connector receptacle JP1 as counting from the left side The MICUSB Dongle has GND labeled on both sides of the adapter board Figure 5 MIC2873 Evaluation Board Interfaces with the MICUSB Dongle EV adapter top side faces down eat Figure 6 Top Side of the Adapter with the Mini Slide Switch Toggled to NOM Position August 25 2014 MIC2873 Evaluation Board MIC2873 Evaluation Software The MIC2873 evaluation software provides a graphic user interface GUI to program the MIC2873 evaluation board A complete application note on the installation and operation of the evaluation software and the USB adapter user manual can be downloaded from Micrel s web site at www micrel com The evaluation software can write to registers inside the MIC2873 IC device via the single wire interface for enabling or disabling the device torch mode flash mode changing the WLEDs brightness in torch mode and flash mode changing the safety timer duration and LED current threshold enabling disabling breath and strobe special effects Getting Started 1 Download the MIC2873 evaluation software and run setup exe file This step may take some time and require an internet connection to update the computer to NET Framework 3 5 2 Install the MICUSB Dongle EV dr
5. sub section the Target OK will be shown up at the status bar at the bottom of the GUI as shown in Figure 8 If the connection is not good the Target Not Detected will be shown up at the status bar and the user has to check with the cable connections before proceeding to the next step When the Target OK status is shown the user can click on the Offline Mode at the menu bar to change it to Direct Editing Mode When the Direct Editing Mode is shown up at the top menu bar and the Direct Editing Mode Active is indicated at the status bar as shown in Figure 9 the software GUI allows the user to control the operation of the MIC2873 evaluation board Introduction to the GUI Panel At the left side of the GUI panel there are different tabs for user to select for specific operations The functions of the tabs are listed below 1 Target Config tab the destination address is shown in this tab User can also click the Test button in this tab to check and establish communication between the evaluation board and PC 2 Registers tab as show in Figure 10 user can check with the MIC2873 registers information and perform on the fly write operation to the IC registers If the user knows the exact valid data value to the registers the data value can be entered to the data edit box corresponding to the target register and then click the Write button When the mouse curser is h
6. Figure 8 MIC2873 Evaluation Software GUI Indicating Target OK at Status Bar Innovation Through Technology File Link Source SWI Help Direct Editing Mode MICAEL r MIC2873 Data Rate 100k bps l Direct Editing Mode Active n Flash Brightness Control Toggle Flash Torch Brightness Control Toggle Torch LED Safety Timer Duration 1250 00ms Thresh 250mA Low Battery Threshold 3 0 V Special Effects Cow OO deter 200 E Figure 9 MIC2873 Evaluation Software GUI in Direct Editing Mode August 25 2014 Revision 1 0 Micrel Inc August 25 2014 File Link Source SWI Help Direct Editing Mode MICAEL r Innovation Through Technology Target Config Registers Options Help _ Registers Operation 54 Read rite T ess Control Toggle Torch Address Hex 01 02 03 04 05 Data Hex 00 00 07 01 04 LED Safety Timer Special Effects on Oe 200 MIC2873 Data Rate 100k bps lp e 4 Direct Editing Mode Active File Link Source gt iY IC2873 E Enabled m i ash Brightness Control Innovation Through Technology Operation Read Torch Brightness Control Address Hex 01 02 03 04 05 Data Hex 00 00 07 01 04 LED Safety Timer Toggle Torch Read Ony O OOO Duration 1250 00ms Thresh 250mA Low Battery Threshold i 30v Special Effects a 0 OT MIC2873 Data Rate 100k bps Direct Editing Mode Active Figure 11 Setting Data Rate from Pulldown Menu
7. JOSE CA 95131 USA TEL 1 408 944 0800 FAX 1 408 474 1000 WEB http Awww micrel com Micrel makes no representations or warranties with respect to the accuracy or completeness of the information furnished in this data sheet This information is not intended as a warranty and Micrel does not assume responsibility for its use Micrel reserves the right to change circuitry specifications and descriptions at any time without notice No license whether express implied arising by estoppel or otherwise to any intellectual property rights is granted by this document Except as provided in Micrel s terms and conditions of sale for such products Micrel assumes no liability whatsoever and Micrel disclaims any express or implied warranty relating to the sale and or use of Micrel products including liability or warranties relating to fitness for a particular purpose merchantability or infringement of any patent copyright or other intellectual property right Micrel Products are not designed or authorized for use as components in life support appliances devices or systems where malfunction of a product can reasonably be expected to result in personal injury Life support devices or systems are devices or systems that a are intended for surgical implant into the body or b support or sustain life and whose failure to perform can be reasonably expected to result in a significant injury to the user A Purchaser s use or sale of Micrel Products for use in li
8. all functions off while consuming minimal power Register settings are reset to default state when coming out of shutdown state In idle mode all register settings persist and all MIC2873 functions continue in their current state Table 1 summarises the difference between the two idle modes Table 1 Differences between Idle Modes 230uUA Voc Low IsuPPLY all functions off 1A Register State Default Persist 100ns Idle mode is entered automatically at the end of a communication frame by holding DC high for Tenp by enabling the device by bringing DC high when in shutdown mode or when an error is detected by the single wire interface logic Shutdown mode can be entered at any time by pulling down DC for 2Tenp discarding any current communication and resetting the internal registers If a communication is received before the shutdown period but after the Tat period the communication is discarded This state is also used to create an internal error state to avoid erroneously latching data where the communication process cannot be serviced in time Additionally each register has a maximum value associated with it If the number of bits clocked in exceeds the maximum value for the register the data is assumed to be in error and the data is discarded August 25 2014 MIC2873 Evaluation Board TEND m Tuar TEND IDLE ey Tush TEND SH root IDLE gt IDLE Figure 2 Abort
9. alues being transferred to the decoder Figure 4 shows an example of entering a write of data 5 to Address 3 ADDRESS DATA FRAME END REGISTER lai LATCH START LATCH WRITE ea ol il al 3 ee Figure 4 Communication Timing Example of Entering Write for Data 5 to Address 3 Only correctly formatted address data combination will be treated as a valid frame and processed by the MIC2873 Any other input such as a single data word followed by Tenp or three successive data words will be discarded by the target hardware as an erroneous entry Additionally any register write to either an invalid register or with invalid register data will also be discarded MIC2873 Registers The MIC2873 supports five writeable registers for controlling the torch and the flash modes of operation as shown in Table 2 Note that register addressing starts at 1 Writing any value above the maximum value shown for each registers will cause an invalid data error and the frame will be discarded Table 2 Five Writeable Registers of MIC2873 Maximum Address Value FEN FCUR Flash Enable Current TEN TCUR Torch Enable Current Description STDUR Safety Timer Duration Low Battery Voltage aed poo Detection Threshold Safety Timer iad Threshold Flash Current Register FEN FCUR default 0 The flash current register enables and sets the flash mode current level Valid values are 0 to 31 values O 15 will set the flash current wit
10. ave reverse polarity protection Applying a negative voltage across the PVIN terminal to PGND terminal can damage the device The MIC2873 evaluation board is tailored for a Li ion range input supply voltage It should not exceed 5 5V on the input MIC2873 Evaluation Board 1 2A High Brightness Flash LED Driver with Single Wire Serial Interface Getting Started 1 Connect external supply to the PVIN terminals Apply desired input voltage to the PVIN J1 and PGND J2 terminals of the evaluation board paying careful attention to polarity and supply range Since the default low battery detection threshold voltage is 3 0V the supply voltage should be set to within 3 0V to 5 5V when testing the MIC2873 without using software via the single wire interface low battery detection threshold can be set to another value or disabled thru software An ammeter may be connected between the power supply positive terminal and the evaluation board PVIN terminal Ensure that the supply voltage is monitored across the PVIN and PGND terminals The ammeter and or power lead resistance can reduce the voltage supplied to the input 2 Enable Disable the MIC2873 The MIC2873 evaluation board has an enable DC pin J4 or JP2 lower pin The MIC2873 is enabled in idle standby mode when the DC pin is asserted high Setting a jumper at JP2 can connect the DC pin to PVIN If this pin is driven low for more than 405us the IC is shutdown Alternatively
11. disabled The LED driver can be resumed by raising the VIN above the LVBD threshold and toggling the corresponding flash or torch command The LBVD threshold is adjustable thru the LBVD control register Address 4 Overvoltage Protection When the output voltage rises above an internal overvoltage protection OVP threshold MIC2873 is latched off automatically to avoid permanent damage to the IC To clear the latched off condition either power cycle the MIC2873 or assert the DC pin low Short Circuit Detection Each time before enabling the LED driver the MIC2873 performs the short circuit test by driving the flash LED with a small 2mA typical current for 200us If Vout Viep lt 1 7V at the end of the short circuit test the LED is considered to be shorted and MIC2873 will ignore the flash and or torch mode command Note that the short circuit test is carried out every time prior to flash and torch mode but the result is not latched Thermal Shutdown When the internal die temperature of MIC2873 reaches 155 C the LED driver is disabled until the die temperature falls below 140 C and either FEN pin FEN register TEN register or VIN is toggled Single Wire Interface The single wire interface allows the use of a single multiplexed enable and data pin DC for control and communication in GPIO limited applications The interface is Implemented using a simple mechanism allowing any open drain or directly driven GPIO
12. fe support appliances devices or systems is a Purchaser s own risk and Purchaser agrees to fully indemnify Micrel for any damages resulting from such use or sale 2014 Micrel Incorporated August 25 2014 13 Revision 1 0
13. hout enabling the flash such that it can be triggered externally values 16 31 will set the flash current and enable the flash August 25 2014 MIC2873 Evaluation Board The flash current register maps into the internal FEN and FCUR registers as shown in Table 3 Table 3 also describes the relationship between the flash current and the FCUR register setting Table 3 Flash Current Register Mapping into Internal FEN and FCUR Registers and Relationship between Flash Current and the FCUR Register Setting FEN FCUR 4 0 Value P_FENFCUR AO Value bec Binary FEN FOUREST a Eoo 0 oo j ao oomo o o0 1 100 Ts ooo 0 oo 1050 a ono 0 0100 1000 Ts coor 0 ow oso e coro o ono oso rz oor 0 om osso Ts oro o 1000 oso o oto 0 1001 orso o oro o 110 0700 ri or 0 to oso a orto o no oso s ono o tor osso a omo o mo owo s om o tm oso l FLAasH A Revision 1 0 Micrel Inc Torch Current Register TEN TCUR default 0 The torch current register enables and sets the torch mode current level Valid values are O to 31 values O 15 will set the torch current without enabling the torch such that it can be triggered by setting the internal TEN register value to 1 values 16 31 will set the torch current and enable the torch A value of O at the internal TEN register will disable the torch The torch current registe
14. iver from FTDI Double click on the file CDM20828_ setup exe The latest driver can be downloaded from the FTDI website www ftdichip com 3 After installing the driver locate the virtual COM port created by the FTDI driver in the Device Manager Menu under Ports COM amp LPT The corresponding port will have FTDI listed as the manufacturer 4 Connect the MIC2873 evaluation board to the PC via the MICUSB Dongle EV Remove the jumpers on JP2 and JP3 on the evaluation board Power the MIC2873 evaluation board PVIN input 5 Set the mini slide switch SW1 on the MICUSB Dongle EV The SW1 should be toggled to the NOM position as shown in Figure 6 6 Open the MIC2873 evaluation software in Programs under the Start Menu Revision 1 0 Micrel Inc Evaluation Software The MIC2873 evaluation software GUI is shown in Figure 7 to Figure 11 When the evaluation software is just Started it is default in offline mode as shown on the right of the top menu bar in Figure 7 The offline mode is only for running the software without the communication or connection with the MIC2873 evaluation board To control the MIC2873 evaluation board with the software GUI the user firstly has to click the Test button in the Target Config tab If the connection from the PC to the dongle and then to the MIC2873 EVB is fine as instructed in Connecting the USB to Single Wire Adapter sub section and in steps 4 and 5 in the Getting Started
15. overing over the register Address Data or Read Only edit check boxes a dynamic tooltips box will show up to indicate the corresponding register name and the functional name of the individual register bits 3 Help tab some hints about the steps for establishing host communications show up inside this tab August 25 2014 MIC2873 Evaluation Board At the right side of the GUI panel which is the MIC2873 control panel user can perform the following MIC2873 operation 1 Check or uncheck the Enabled option to enable or disable the MIC2873 device 2 Adjust the flash brightness with the Flash Brightness Control slide bar from 1 2A to 0 25A in16 steps with The maximum is on the left and the minimum is on the right 3 Fire flash or reset flash by clicking the Toggle Flash button 4 Adjust the torch brightness with the Torch Brightness Control slide bar from 300mA to 62 5mA in 16 steps The maximum is on the left and the minimum is on the right 5 Set or reset torch by clicking on the Toggle Torch button 6 Change the LED Safety Timer duration setting from 156ms to 1250ms with 8 options Change the LED Safety Timer LED current threshold from 100mA to 300mA in 50mA step The LED Safety Timer can also be disabled by setting the LED current threshold to the Disable option Please refer to Table 5 and Table 7 for details 7 Set the Low Battery Threshold voltage from 3 0V to 3 8V in 0 1V ste
16. p The low battery threshold function can be disabled by choosing the Disabled option 8 Click the Breath button Strobe button and set delay time options for special effects demonstration Setting of Single Wire Interface Data Rate The data rate of the single wire interface communication can be set at the pull down menu from the SWI menu at the top menu bar as shown in Figure 11 User can set the data rate to 100kKHz 1MHz 3MHz or 6MHz from the pull down menu Revision 1 0 Micrel Inc File Link Source SWI Help MICAEL r Innovation Through Technology MIC2873 Evaluation Board MIC2873 Flash Brightness Control Toggle Flash LED Safety Timer Duration 1250 00ms Thresh 250mA Low Battery Threshold 3 0 Vi Special Efects 8 delet 200 E Figure 7 MIC2873 Evaluation Software GUI Initial Start Up Window in Offline Mode File Link Source SWI Help MICAEL r Innovation Through Technology Target Config Registers Options Heb Destination Address Qx 00 Ob 0000000x Register Polling Enable Period ms sok Address FFF EH FFF FFF Cy MIC2873 Data Rate 100k bps Target OK MIC2873 E Enabled Flash Brightness Control Toggle Flash Torch Brightness Control Toggle Torch LED Safety Timer Duration 1250 00ms Thresh 250mA Low Battery Threshold 3 0 VH Special Effects ona oe dt 200 EE
17. r is disabled Table 6 shows the threshold values that correspond to the register settings Setting O is reserved for disabling the function and settings between 1 and 9 inclusively enable and set the LB TH value between 3 0V and 3 8V with 100mV resolution Table 6 Low Battery Threshold Register Setting and Supply Threshold Voltage LB_ TH 3 0 Veat Threshold V Value Dec Binary 00 0010 3 1 0011 0100 600 o 010 or 100 6 8 ES August 25 2014 MIC2873 Evaluation Board Safety Timer Threshold Current Register ST_TH Default 4 Safety timer threshold current determines the amount of LED current flowing through the external LED before the internal LED safety timer is activated Setting ST_TH to 0 disables the safety timer function and setting the register to values 1 to 5 set the safety time threshold current 100mA to 300mA in 50mA steps Table 7 Safety Timer Threshold Current Register Setting and Safety Timer Threshold Current Value Safety Timer Threshold ST_TH 2 0 ay MC re 0 ooo o0 Disabled 001 001 Revision 1 0 Micrel Inc Evaluation Kit Overview The MIC2873 can be operated as a standalone board or as a modular system where the evaluation board is connected to a PC via single wire to USB interface board MICUSB Dongle EV Connecting the USB to Single Wire Adapter When interfacing the MIC2873 evaluation board with the MICUSB Dongle carefully match the GND pin of the
18. r maps into the internal TEN and TCUR registers as shown in Table 4 Table 4 also describes the relationship between the torch current and the TCUR register setting August 25 2014 MIC2873 Evaluation Board Table 4 Torch Current Register Mapping into Internal TEN and TCUR Registers and Relationship between Torch Current and the TCUR Register Setting TEN TCUR 4 0 Value O TENTCURIED Value rec ae seme Teoma aaa m1 Fever 0 ooo ears a oot o oo 2750 e ooo 0 oon asa 4 oot 0 0100 2500 Ts oot 0 om ars e ooo o ono 250 Dr Poot 0 om aes Ts oo o 1000 2000 rs oor 0 too 17s rio oo 0 10 1750 rir om 0 ton teas rie orto o mo 1500 rie font 0 no tars re fon 0 m0 oo ms fon o mm eas Revision 1 0 Micrel Inc Safety Timer Duration Register STDUR Default 7 The safety timer duration register sets the duration of the flash and torch mode when the LED current exceeds the programmed threshold current Valid values are O for the minimum timer duration to 7 for the maximum duration Table 5 Safety Timer Duration Register Setting and Safety STDUR 2 0 Timer Duration i Timeout ms binary Value Dec Binary _ o o oo 15625 ef mo 0 os Low Battery Threshold Register LB_ TH Default 1 The LB_TH register sets the supply threshold voltage below which the internal low battery flag is asserted and the LED current drive
19. the IC can be enabled or disabled by software through single wire interface 3 Enable Disable the flash mode The FEN J5 or JP3 lower pin is the flash mode enable pin A low to high transition at this pin initiates the flash mode and the safety timer Setting jumper at JP3 can connect FEN to PVIN If FEN pin is left floating it will be pulled down internally by built in 14A current source when the device is enabled Alternatively the flash mode can be enabled or disabled by software through single wire interface 4 Graphic user interface support Graphical user interface software can be used with the MICUSB Dongle EV for configuring and testing of the MIC2873 with a standard computer For more detail refer to the MIC2873 Evaluation Software section Ordering Information MIC2873YCS EV MIC2873 Evaluation Board MICUSB IC Serial Programmer Board Micrel Inc 2180 Fortune Drive San Jose CA 95131 USA tel 1 408 944 0800 fax 1 408 474 1000 http www micrel com August 25 2014 Revision 1 0 Micrel Inc Evaluation Board Description a ff ICREL Inc eee n a wf MIC28 f 3 Y CS pi F aii Figure 1 MIC2873 Evaluation Board Flash Mode The maximum current level in the flash mode is 1 2A The flash mode current can be initiated by asserting FEN pin high or by setting the flash control register Address 1 through the single wire interface for the desired flash duration subjected to the safet
20. to control the MIC2873 The MIC2873 uses the single wire interface for simple command and control functions The interface provides fast access to write only registers with protection features to avoid potentially erroneous data writes and improve robustness When DC is in a low state and no data is detected for longer than 405us the MIC2873 will automatically go into a low power SHUTDOWN state simultaneously resetting internal registers to default states Revision 1 0 Micrel Inc Overview The single wire interface relies on a combination of bit edges and the period between edges in order to communicate across a single wire Each word is transmitted as a series of pulses with each pulse incrementing an internal data counter A stop sequence consisting of an inactive period of DC pin remaining high is used to latch the data word internally An address and data framing format is used to improve protection against erroneous writes by enforcing address and data field lengths as well as the timing duration between them Timing is designed such that when communicating with a device using a low cost on chip oscillator the worst case minimum and maximum conditions can be easily met within the wide operating range of the oscillator Using this method guarantees that the device can always detect the delay introduced by the communication master Idle States and Error Conditions In shutdown mode the MIC2873 is in a reset condition with
21. y timeout setting The flash mode current is terminated when the FEN pin is brought low and the flash register is cleared or when the configurable safety timer expires Flash mode current can be adjusted to a fraction of the maximum flash mode current level by selecting the desired value in the flash control register through the single wire serial interface Torch Mode By default the maximum torch mode level is 300mA The torch mode operation is activated by setting the torch control register Address 2 for the desired duration The torch mode current is terminated when the torch register is cleared or when the configurable safety timer expires Like the flash mode current the torch mode current can be set to a fraction of the maximum torch mode current level by selecting the desired torch current in the torch control register Address 2 through the single wire serial interface Configurable Safety Timer The safety timeout feature automatically shuts down the LED current after the safety timer duration is expired if the programmed LED current exceeds a certain current threshold Both the current threshold and the timer duration are programmable via the safety timer registers Addresses 3 and 5 August 25 2014 MIC2873 Evaluation Board Low Battery Voltage Detection LBVD When the VIN voltage drops below the low battery voltage detection LBVD threshold default 3 0V in flash or torch mode the LED current driver is
Download Pdf Manuals
Related Search