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X72 Rubidium Oscillator

1. Symmetricom X72 Rubidium Oscillator Designer s Reference and User Guide Revision A November 2004 Part Number 097 10603 01 Symmetricom Inc 2300 Orchard Parkway San Jose CA 95131 1017 U S A http www symmetricom com Copyright 1999 2004 Symmetricom Inc All rights reserved Printed in U S A All product names service marks trademarks and registered trademarks used in this document are the property of their respective owners Contents Purpose ot This Gunde aura Rae pu chee ee 12 Who Should Read This 12 Str cture OF THIS Guide os 5 eee bt doh Chee 12 Conventions Used in This 13 Warnings Cautions Recommendations and Notes 14 Related Documents and Information 15 Where to Find Answers to Product and Document Questions 15 What s New In This 15 Chapter 1 Description so Se te uns Mok es abes Data fue Pc de 18 Typical Applications us oor a aei ea S NOS PR RC S e adis eto tp dut een Ne 19 SPECIIGANOMS ou o e race ioco eger Widest cde do oo Ba E e apiid daa dcr 21 Chapter 2 Design Integration Considerations Mechanical 5 lt
2. 9 0 0 0 1 0 2 0 3 0 4 nS ns 54 3 CONSTANT MEN REMOVE CONSTANT Po CON sc a PARAE E E 2 0 if both PPS amp data FRE Q OFFSET Plat options A 3295 em m 5 1 1 0 10 0 0E 0 dff 1 0 10 pam S Bu 0 0 0 1 0 2 0 3 0 4 0 5 dif seconds sample amp oHPPSRecords ofdifRecoris 0 1 0 if MO PPS data USE VINDOWS SHOW IINFO FOR OPERATING INSTRUCTIONS 839 839 E qm 720032 Figure D 4 Flywheeling Recover with 1PPS offset gt 1 In this test the antenna to the GPS receiver is removed The X72 is purposely put off frequency long enough to induce a 1PPS error over 1 When the antenna is reapplied the X72 1PPS recovers by resetting to 1PPS 0 nanoseconds JamSynch This procedure was repeated to cause both a leading and lagging 1PPS Note This test was performed on a unit started cold which is what causes the general curve in the frequency data excluding the intentional offsets 86 X72Desiger s Reference and User s Guide 097 10603 01 Rev A November 2004 72 1 Algorithm Theory of Operation X72 1PPS Algorithm Theory of Operation X72 qualifies 1 pulse per second inputs by analyzing the time difference between the X72 s 1PPS output and the external 1PPS input This is referred to as the HoldOver state The X72 d
3. ol N gt N po pol BR ole 6 e gu n 3 EN 29 24 25 N N 4 WIRING DIAGRAM NOTE PINS 25 amp 26 TWISTED 3 TURNS INCH X720021 3 25 Inch Interface Cable Connections 097 10603 01 Rev November 2004 X72 Desiger s Reference and User s Guide 55 Edge Board Layout Drawing Edge Board Layout Drawing a 100 16X 0 041 002 AFTER PLATING 3X 3 250 100 5 956 2X 2 750 8X 3 213 SUGGESTED PCB LAYOUT X72 UNIT E ANCHORED Pe 0 EDGE BOARD P N 106569 002 1 e e e 3 50 STANDARD EDGE BOARD P N 106569 001 3 51 70 720022 Figure A 5 Layout Drawing for Edge Board 56 X72 Desiger s Reference and User s Guide 097 10603 01 Rev November 2004 Appendix Symmetricom Serial Interface Protocol This appendix provides information on communicating with the X72 through serial port J1 It includes output examples and a description of commands In This Appendix a Using the Symmetricom Serial Interface Protocol 097 10603 01 Rev November 2004 X72 Desiger s Reference and User s Guide 57 Using the Symmetricom Serial Interface Protocol Using the Symmetricom Serial Interface Protocol The Symmetric
4. Caution The X72 has no reverse voltage protection and damage will A occur if power is applied to the unit in reversed direction m Verify that the X72 is mounted to the heat sink supplied or to a customer supplied heat sink device m Verify that the power supply is set to the correct voltage if adjustable and is unplugged a Connect the X72 to a properly terminated shielded cable that does not have power applied Once the unit has been properly terminated plug in the cable to the power supply Figure C 1 shows a block diagram of the suggested X72 test setup Note Sine filter Capacitor required PC COM Port SCOPEOR SPECTRUM ANALYZER di 50 OHM Adapter Test Board J4 B DVM 90 264 Vac 47 63 H 63 Hz vss 720023 Figure C 1 Suggested X72 Test Setup Once The X72 is plugged in and receiving power wait 3 to 4 minutes while the unit achieves atomic lock During this period the monitored LOCK signal should be HIGH Once the unit achieves atomic lock the LOCK signal goes LOW 097 10603 01 Rev November 2004 X72 Desiger s Reference and User s Guide 69 Symmetricom Serial Interface Protocol SSIP Depending on base plate temperature within 4 to 8 minutes the unit should be within 1xE of center frequency Thirty minutes after applying power to the X72 the rf output frequency will be very close to full accuracy refer to X72 specific
5. FSINERTN SPECTRUM lt 4 from device pin ANALYZER i pers FACMOS FACMOSRTN coe Sees 2 LOCK DVM 720015 Figure 3 1 Suggested Connections for X72 Initial Turn on 44 X72 Desiger s Reference and User s Guide 097 10603 01 Rev November 2004 Installation and Operation Start up Sequence Once the X72 is plugged in and is receiving power wait 3 to 4 minutes while the unit achieves atomic lock During this period the monitored LOCK signal should be HIGH Once the unit achieves atomic lock the LOCK signal goes LOW Depending on base plate temperature within 4 to 8 minutes the unit should be within 1xE of center frequency Thirty minutes after applying power to the X72 the rf output frequency will be very close to full accuracy refer to X72 specifications Note The output frequency of the X72 is more accurate than most counters Appropriate measurement equipment can be obtained from Symmetricom Inquire with Symmetricom Marketing or your local sales representative about Symmetricom s line of test and measurement standards which includes the PRFS and FMS 2001 Start up Sequence When power is connected to connector J1 the X72 begins its warm up cycle After four minutes the rubidium oscillator reaches a locked condition and its output signals will stabilize The accuracy at shipment is lt 5xE711 at 25 C typical Note Signals appear at the outputs
6. Index A a command 60 accuracy of signal 45 ACMOS output frequency 37 adapter LPRO 33 administrative mode commands 62 bandpass 36 base plate temperature 34 baud rate 58 Built in Self Test BIST 20 cable 68 3 25 inch 32 68 customer supplied 73 interface 73 shielded 28 capacitor 29 15 uF 30 31 390 pf 30 31 36 coupling 36 filter 33 69 cautions defined 14 CDMA 19 cellular 19 comm port 58 command control status dialog 20 commands 58 a 60 administrative mode 62 factory mode 62 h 59 help 59 159 60 run mode 58 62 w 60 communication parameters baud rate 58 data rate 58 connectors 68 mating 28 contamination 35 control register 65 coupling capacitor 36 data rate 58 digital network timing 19 documentation related 15 edge board 29 anchored 31 standard 30 unpopulated 29 embedded controller 20 ESD 35 external timing reference 19 factory mode 61 factory mode commands 62 FC mode 60 filter capacitor 33 filtering optimum 40 firmware 20 45 48 73 firmware upgrades 48 FLL 47 floating point format 61 frequency control 38 frequency control signal 37 frequency output 40 frequency locked loop 47 G GPS 19 h command 59 heat sink 34 69 73 heater circuits 20 help command 59 i command 59 interface cable 73 097 10603 01 Rev November 2004 X72 Desiger s Reference and User s Guide 95 L V interface test board 73 L LOCK alarm si
7. f 2 Values less than this are ignored Maximum frequency charge is not constrained Setting the frequency outside of its operating limits may render the unit non functional 097 10603 01 Rev November 2004 X72 Desiger s Reference and User s Guide 39 Design Integration Considerations X72 Susceptibility to Input Noise X72 Susceptibility to Input Noise If you have an application where the output spectrum phase noise and spur integrity is crucial the X72 must have a comparatively clean source of dc power free of spurious current or voltage noise Connecting fans heaters and other switching devices to the dc supply powering the X72 can result in degraded phase noise and spur performance Best performance is achieved with only one output turned on and the other frequency outputs turned off The Rb atomic frequency source uses a modulation demodulation lock in amplifier scheme with a modulation frequency of approximately 156 Hz Inherent in this approach is sensitivity to noise at multiples of the modulation frequency This noise is coupled through both the heater and electronic power lines to cause modulation spurs on the output frequency Note Avoid the modulation frequency and its lower harmonics roughly up to the tenth harmonic The X72 has an internal dc to dc converter supplying power to the critical electronics including the crystal oscillator which is the source for the outputs Input Filtering If
8. 28 Mounting Recommendations 28 Recommended Mating Connectors 28 Integrating the X72 into a 29 Thermal Considerations 2 352 cote ee us wb De ac eee sale We 34 Thermal Tae caes OCCORRE Ed ea 34 Water Condensation and Excessive Humidity 35 Excessive aoe qu E cona ba Gore Pct oe 35 External Interfaces and Grounding 35 Electrical Interface m ubt hs 36 Outputs been 36 X72 1 PPS Input Output edu edu soe ede due Es 36 le adi dft Tod 36 53 Sin Erg PS d al Aes Gad 37 X72 Frequency Control Signal 222 2220 06 bee ee eee ees 37 X72 ACMOS Output Frequency 37 Frequency Control Analog s as tue wen pate pA ym UE 38 Greater Than 1xE 9 Internal or External Control 38 Time Response of External Frequency Control 38 Temperature Compensation of 38 Modifiable Unit Settings 39 097 10603 01 Rev November 2004 X72 Desiger s Reference and User s Guide 3 X7
9. Note ADMIN mode allows the loading of new code or updates or reconfiguring defaults in the field It is not a normal operating mode The output control status register OSR bit structure control features and controlling factors are defined as shown below Table B 5 Output Control Status Register Structure Bit Control Description Controller 0 Lamp Switch Power 1 Lamp Switch is on Controlled by firmware Automated Boost internal unit 0 Lamp Switch off Function function 1 BIST Output 0 Unit is locked Controlled by firmware Automated 1 Unit is not locked Function 2 FXO Enable 0 Enable FXO output Default is set at Factory per Configuration file 1 Disable FXO output that matches customer s selection Host can alter during operation but host cannot alter the default power up condition 3 1PPS Output 0 Enables 1PPS Default is set at Factory per Configuration file Enable Output that matches customer s selection Host 1 Disables 1PPS can alter during operation but host cannot Output alter the default power up condition 64 X72Desiger s Reference and User s Guide 097 10603 01 Rev A November 2004 Using the Symmetricom Serial Interface Protocol Table B 5 Output Control Status Register Structure Continued Bit Control Description Controller 4 ACMOS Output 0 Enable Output Default is set at Factory per Configuration file Enable 1 Disables Output that mat
10. 5 64 Output Control Status Register 64 Connector J1 Signal Information 71 1PPS States Returned with the j Command 83 1PPS Firmware 51 5 84 097 10603 01 Rev November 2004 X72 Desiger s Reference and User s Guide 9 10 X72 Desiger s Reference and User s Guide 097 10603 01 Rev A November 2004 How to Use This Guide This section describes the format layout and purpose of this guide In This Preface m Purpose of This Guide Who Should Read This Guide m Structure of This Guide a Conventions Used in This Guide Warnings Cautions Recommendations and Notes mw Related Documents and Information a Where to Find Answers to Product and Document Questions What s New In This Guide 097 10603 01 Rev A November 2004 X72 Desiger s Reference and User s Guide 11 Purpose of This Guide Purpose of This Guide The X72 Designer s Reference and User s Guide provides basic recommendations for designing products to use Symmetricom s X72 Rubidium Oscillator The guidelines in this user guide are generic because specific product requirements vary from application to application This material consists of a brief description of X72 design supported by block diagrams description of environmental issues installation guideline
11. removed If the unit no longer operates properly or if it has reached the end of its effective life please visit Symmetricom s web site at www symmetricom com and click the support warranty and repair link You can also type the following link into your computer www symmetricom com support warranty_and_repair repair_form aspx prodtype TSD Once you submit your form through the Internet a confirmation will be sent back to you Requests are processed within 24 to 48 hours Once processed you will receive an e mail from the Repair Administration group that provides your RMA number warranty information or repair cost if applicable and the address of where to send the unit for repair If you have questions regarding the status of your RMA you may reach our Repair Administration department at 888 367 7966 option 3 You may also e mail your requests or queries to TSDRMA Symmetricom com Our fax number is 559 961 5175 48 X72 Desiger s Reference and User s Guide 097 10603 01 Rev November 2004 Installation and Operation Repairs X72 Warranty Symmetricom warrants the X72 electronics for one year and the Rb lamp bulb and resonator cell for 20 years Symmetricom also warrants that at the time of shipment the X72 will be free from defects in materials furnished and workmanship performed by Symmetricom This warranty and Symmetricom s liability are limited to either granting credit or repairing or replacing at seller s option
12. with reasonable promptness after return to Symmetricom of any article that is disclosed to Symmetricom s satisfaction to be defective and only if said article is returned to Symmetricom promptly after discovery of such defect and in no event later than 12 months or such other time period as may be specified in writing as a warranty period for a particular article from the date of delivery thereof Normal transportation charges in connection with an article returned shall be at the Symmetricom s expense but only if Symmetricom is responsible under the terms of this warranty This warranty does not extend to any article which has been subject to misuse neglect or accident nor does it extend to any article which has been repaired or altered by other than the seller or operated outside the published maximum temperature ratings THIS WARRANTY IS IN LIEU OF ALL OTHER WARRANTIES EXPRESSED OR IMPLIED INCLUDING ANY WARRANTY OF FITNESS FOR A PARTICULAR PURPOSE AND THE RIGHTS AND REMEDIES PROVIDED HEREIN ARE EXCLUSIVE AND IN LIEU OF ANY OTHER RIGHTS OR REMEDIES IN NO EVENT SHALL SELLER BE LIABLE FOR CONSEQUENTIAL DAMAGES 097 10603 01 Rev A November 2004 X72 Desiger s Reference and User s Guide 49 Installation and Operation Repairs 50 X72 Desiger s Reference and User s Guide 097 10603 01 Rev November 2004 Appendix A 72 Connector and Plug This appendix provides information on the Molex connector and plug the edge
13. 3 cable 720028 Figure C 6 X72 Interface Options 097 10603 01 Rev November 2004 X72 Desiger s Reference and User s Guide 75 X72 Development Kit Hardware 76 X72 Desiger s Reference and User s Guide 097 10603 01 Rev November 2004 Appendix D One Pulse Per Second Source Connection This appendix describes how to connect a one pulse per second 1PPS source such as a commercial GPS receiver to an X72 to achieve long term accuracy and excellent holdover or flywheeling performance In This Appendix a Connection Requirements m Background X72 1PPS Functions m System Requirements m X72 1PPS Algorithm Operation m Setting the X72 for 1PPS Synchronization m 1PPS Firmware Versions a Flywheeling Recovery Normal Recovery with JamSynch X72 1PPS Algorithm Theory of Operation 097 10603 01 Rev A November 2004 X72 Desiger s Reference and User s Guide 77 Connection Requirements Connection Requirements The following connections are required for 1PPS setup Power a GPS antenna 1 from the source to the X72 No serial port communication is required for initial setup unless you want to make changes from the factory default settings Information on setup operation and integration is provided This document applies to X72s manufactured after November 2003 with customer firmware versions 5 02 or higher see Table D 2 for applicable versions Background GPS techno
14. Rev November 2004 X72 Desiger s Reference and User s Guide 43 Installation and Operation Installation Installation Site Selection The X72 can be mounted in any orientation In environments that approach the operating limits of the X72 ensure that the temperature limits are not exceeded The X72 is sensitive to external dc and ac magnetic fields refer to specification and should not be installed in locations subjected to strong magnetic fields from transformers or large power supplies An external magnetic field under 2 gauss should not result in measurable frequency offsets for X72 A Rb frequency standard is a very precise component and you should employ optimum practices for its use Avoid using a power source that is also providing power to fans or equipment that generates high current pulses Turn on Procedure Use the following steps to power up the X72 Caution To avoid damage to the X72 do not apply power to the unit A in reversed direction The X72 has no reverse voltage protection 1 Verify the X72 voltage requirement 10 to 32V 2 Verify that the power supply is set to the correct voltage and is turned off 3 Connect J1 of the X72 to a properly terminated shielded cable that does not have power applied 4 Once the unit has been properly terminated turn on power Refer to Figure 3 1 for a block diagram of a suggested hook up PWR dd ges SCOPEOR 24V NOM
15. SMT rf transformer X72 1 PPS Input and Output The 1 PPS output signal of the X72 unit is positive edge triggered and gated with the rising edge of the clock Its duration for 10 MHz unit is 400 ns 10 Rise fall time is 4 ns The 1 PPS is exactly divided from the XO frequency Lock Signal The LOCK signal indicates that the internal Voltage Controlled Crystal Oscillator VCXO is locked to the atomic transition If the Lock signal is LOW once warm up is completed the output frequency is locked to the Rb atomic clock 36 X72Desiger s Reference and User s Guide 097 10603 01 Rev A November 2004 Design Integration Considerations Electrical Interface If the LOCK signal is high atomic lock has been lost and the X72 goes into sweep mode to reacquire lock The sweep ranges from approximately 21 ppm to 21 ppm in approximately a 20 second period During the sweep outputs are maintained but you should not rely on signal accuracy during sweeping If the power source to the X72 is OFF the lock output line is low Service Signal The Service Signal is valid when the unit is operating and the rubidium oscillator is locked The Service Signal algorithm monitors the health of the Rb physics package which includes the Rb lamp bulb and resonator cell and the unit s crystal oscillator that is slaved to the Rb atomic clock The Service Signal indicates low when any of the internal operating parameters are near the end of the
16. and long term stability and excellent spur performance Note Symmetricom s commitment to quality and reliability is backed by a 20 year warranty on the physics package lamp bulb and resonator cell The microprocessor based X72 is a more cost effective system design that allows serial command selection and enabling of TTL level digital output frequencies This allows the oscillator output to be divided to a number of different frequencies as opposed to older oscillators with a single fixed output frequency The sine output frequency is selected at time of order A 1 PPS output is an integral part of the design An optional 1 PPS input allows the unit to track a GPS or other external reference and display the difference between the input and the 1 PPS generated by the X72 through the RS232 link 097 10603 01 Rev A November 2004 X72 Desiger s Reference and User s Guide 19 Description Typical Applications For simple applications the X72 provides a 5V CMOS compatible Built in Self Test BIST Service and a LOCK alarm signal derived from the basic physics operation This lock signal indicates when the output frequency is locked to the atomic resonance of rubidium When more control over the device is desired an extensive command control status dialog is available In addition to controlling the operation of the oscillator the microprocessor s built in firmware allows an external host computer to communicate with the embedded c
17. e 126 to 1 9999998 127 where e represents 2 to the power of 097 10603 01 Rev A November 2004 X72 Desiger s Reference and User s Guide 61 Using the Symmetricom Serial Interface Protocol The serial interface is initialized as follows Table B 2 defines the X72 s Run Mode Commands Table B 3 defines the bit functions of the factory mode commands of the X72 Table B 4 defines the administrative mode commands Table B 5 defines the bit functions and controlling agent of the output control register of the X72 Table B 2 Run Mode Commands Response to User Output to X72 Host Command Name and Description Command DATA a Set FC mode To be Specified Set Analog Frequency Control Mode Example a lt zero or This command toggles the analog input non zero integer gt pin to the unit Freq Cntl between enable cr and disable In Factory mode the default is enabled During factory test the default is set to disable for shipping unless the customer ordered the default to be set enabled f Desired frequency change be Specified Adjust Frequency from free running center Adjust Unit output frequency Used to frequency in parts to p discipline the unit The smallest Example for a 100xE f incremental frequency change is 2xE 4 change 100 lt gt or f 2 Any value less than this will still 11 be used value that can be used at Example a 100xE ee 8 M on
18. immediately after power is applied to the unit but these output signals are not stable until after the oscillator has locked After 7 5 minutes the accuracy of the X72 oscillator is lt 1 9 Performance of the X72 unit varies according to the application profile specified by the customer at time of order Refer to the X72 product specification for information on application profiles and unit performance To monitor performance and selectively modify it using the SSIP firmware included in the unit connect the unit to the COM port of a PC running Windows 097 10603 01 Rev November 2004 X72 Desiger s Reference and User s Guide 45 Installation and Operation Start up Sequence Dialog OK Serial 1 second Interface Mute maximum 17W Interval varies based on Quiescent Operation temperature 45W of unit at turn on Typically Level varies from 5 W to 15 W Power requires less than a minute depending on temperature of unit TTL high Osc Lock The lock signal goes low once the unit has completed its warmup cycle 4 minutes TTL low active Outputs become present after the RS 232 baud rate is established 2 4 seconds Outputs Present off Service qr e 155 i 1 Signal Service signal is valid after oscillator has locked is valid i 2 4seconds 6secs 4 minutes Elapsed Time X720016 Figure 3 2 Se
19. lt MOLEX Connector Imm 3 250 82 6 P N 52629 2651 Mate with MOLEX e e P N 52660 2651 shown below 238 Base Plate Connector Pin Outs 69 9 3 00 VDD VDD 76 VDD VDD VDD VDD VDD SERVICE DOUT DIN FREQ CNTL vss VSS VSS VSS 1 PPS IN LOCK FACMOS RTN FACMOS OUT FSINE RTN FSINE OUT CAUTION Unit has no reverse voltage connection e Y Bottom View 2 07 Dimensions in inches mm 52 5 Cs A Cle 3 0 42 10 7 Front View Y X720004 Figure 1 4 X72 Dimensions and Connector Pin Assignments are properly connected This unit has an internal fuse but has no Caution To avoid damage to the X72 ensure that power and ground reverse polarity protection Note All pins on the MOLEX connector must be connected 097 10603 01 Rev November 2004 X72 Desiger s Reference and User s Guide 21 Description Specifications Table 1 1 X72 Design Absolute Maximum Ratings Pin r 1 Number Signal Name Type Signal Function 1 7 VDD PWR Power input 10 to 32 Vdc all power pins must be connected 8 SERVICE Output Indicates unit is nearing limits of frequency control and that Service is required within several months 9 DOUT Output UART data out at ACMOS logic levels 10 DIN Input UART data in at ACMOS logic levels 11 FREQ CTRL Analog Frequency control analog input between 0 5 Vdc 12 18 VSS GND Power amp
20. of an interface test board with connectors a heat sink a 3 25 inch 8 25 cm cable a 3 foot 0 914 M interface cable and product documentation An optional power supply can be ordered The output or input of each connector is identified on the board A photo of the interface board is shown in Figure C 4 E Note 10 to 32 Vdc is the recommended method of operation To use the SSIP firmware of the X72 connect the serial port of the interface test board to a host PC com port this cable is supplied by the customer Refer to Using the Symmetricom Serial Interface Protocol on page 58 for information on SSIP commands and responses 1 PPS output Sine output Crystal Frequency Output ACMOS Frequency Output 720026 Serial Port to External PC Figure C 4 Top View of X72 Test Interface Board 097 10603 01 Rev November 2004 X72 Desiger s Reference and User s Guide 73 X72 Development Kit Hardware X72 Adapter Test Board Side View Supplied Interface Cable 106452 001 Heat Sink P N 106494 001 for use during high temp tests Cable to Main ac Power 24 Vdc nom Optional External 90 to 264 Vac Power Supply VID 040029 001 Power Supply Cable 6 BNC 1 PPS Input Oscillator Reference NOTES A Pins enable BIST and analog input B Pins enable 10 24 Vdc operation P N 106031 XXX Supplied Interface Cables 3 P N 060032 001
21. signal return all grounds must be connected 19 1 PPS IN Input 1 PPS input positive edge triggered 20 1 PPS OUT Output 1 PPS output may be enabled disabled digitally 21 LOCK Output If low indicates Rb osc is locked 22 FXO Output FXO ACMOS output equalling the VCXO frequency 23 FACMOS GND Return for FACMOS amp FXO signals RTN 24 FACMOS Output FACMOS ACMOS output option equals OUT VCXO frequency divided by 2xN N is selectable 25 FSINE RTN GND Chassis ground return signal for FSINE signal 26 FSINE OUT Output FSINE Sine output option equals VCXO frequency divided by 2xM M is set at the factory Note 1 All inputs and outputs are ESD protected short circuit protected and all inputs are compatible with 3 3V ACMOS logic and 5V TTL logic 2 High impedance Note Refer to Appendix A for the connector manufacturer s drawings and specifications 22 X72 Desiger s Reference and User s Guide 097 10603 01 Rev November 2004 Table 1 2 X72 Design Absolute Maximum Ratings Description Specifications Characteristic 40 85 Symbol Unit in ambient still air convection Base plate Units Vcc Supply relative to ground 10 to 32 volt unit 0 25 to 40 Vin Input voltage relative to DIN amp 1PPSIN 0 5 to 5 5 V ground regardless of power supply voltage Frequency control 0 5 to 5 5 Pwu Max Warm Up Po
22. the X72 edge board and 3 25 inch 8 255 cm cable 12 X72 Desiger s Reference and User s Guide 097 10603 01 Rev A November 2004 Conventions Used This Guide Chapter Title Description Appendix B Symmetricom Serial Interface Protocol This appendix describes use of the external communications link software Appendix C Using the X72 Developer s Kit This appendix describes the X72 developer s kit hardware Index Provides references to individual topics within this guide Conventions Used in This Guide This guide uses the following conventions a Acronyms and Abbreviations Terms are spelled out the first time they appear in text Thereafter only the acronym or abbreviation is used a Revision Control The title page lists the printing date and versions of the product this guide describes a Typographical Conventions This guide uses the typographical conventions described in the table below When text appears this way it means X72 Rubidium Oscillator User s Guide The title of a document LOCK An operating mode alarm state status or chassis label Press Enter A named keyboard key The key name is shown as it appears on the keyboard An explanation of the key s acronym or function immediately follows the first reference to the key if required FC mode enabled Text in a source file or a system prompt or other text that appears on a
23. user to track indications of pending end of life for the unit with sufficient warning to avoid a total and sudden failure of the unit The key indicator of health is the service indicator that indicates when the Rb physics package or on board quartz oscillator are near their operating or control limits If the Lock signal does not indicate a Rb lock within the specified time or the Service signal indicates that the unit has reached the end of its effective life remove the unit and return to Symmetricom for service The Service indicator is valid only when the Lock signal indicates that the unit is locked For information on how to return a unit for service see Repairs on page 48 097 10603 01 Rev November 2004 X72 Desiger s Reference and User s Guide 41 Design Integration Considerations X72 Reliability and Maintenance 42 X72 Desiger s Reference and User s Guide 097 10603 01 Rev November 2004 Installation and Operation Chapter 3 Installation and Operation This section provides information on details to consider when installing the X72 and the procedure to follow when turning on the unit There is an explanation of the start up sequence monitoring performance and theory of operation It also contains a troubleshooting guide customer support information and warranty information In This Chapter Installation Start up Sequence Theory of Operation m Troubleshooting m Repairs 097 10603 01
24. 2 Susceptibility to Input 40 Input FIltenmngiz 25 5 9 3 p oa one metu Rod 40 X72 Reliability and 41 i25 or a oce oa ede o SR quib rariss dre Ut 41 Maintenance eg hs ees 41 Chapter 3 Installation and Operation IIS fa ANON Sakae 44 Site Selection iu 6 318 s 44 Turn on Procedure 44 Start Up SEQUENCE 45 Theory OF 6 57 cea e qo Ef i aia ac Io e a quc wes E 47 Troubleshooting mbi rop ed 48 48 nle ane tren PDOs d eae dus Wh aod Ee cs Cals ad A 49 Appendix A X72 J1 Connector and Plug Molex Connector Rad X Ri Aqu d REESE 52 Molex Connector Plug Assembly 53 Edge Board PINOUT 54 3 25 Inch Interface Cables 5 258 OR wie Sand 55 Edge Board Layout 56 Appendix Symmetricom Serial Interface Protocol Using the Symmetricom Serial Interface 58 Host Terminal Emulator Setup 58 Data et cada Rap in ug ane e a aise be 58 Factory MOOG uie 43 Kees 2g 30487 61 Floating Poin
25. 7 10603 01 Rev A November 2004 warnings defined 14 warranty 19 48 web address 15 w command 60 wireless 19 warm up cycle 45 097 10603 01 Rev November 2004 X72 Desiger s Reference and User s Guide 97 98 X72 Desiger s Reference and User s Guide 097 10603 01 Rev November 2004
26. 720018 Molex Connector Figure A 1 097 10603 01 Rev A November 2004 52 X72Desiger s Reference and User s Guide Molex Connector Plug Assembly Molex Connector Plug Assembly UG 20 s eee TOM 2 m gt gt 8 85 8 mes 1 1 in me o IN reo LAD Olo als e ox LAC 0 i Te Bo BN s co co N x ale eg zoo c o E 5 eu N BI N a gt a 7 o e Qs 5 2 o ora 3 2 JN o aw 720019 Figure 2 Molex Connector Plug Assembly 097 10603 01 Rev November 2004 X72 Desiger s Reference and User s Guide 53 Edge Board Pinout Edge Board Pinout X72 Connector Cable Connector P1 VIN VIN D_OUT SERVICE CFIELD D_IN GND GND 1PPS IN 1PPS OUT LOCK XTAL OUT ACMOS GND ACMOS OUT RF GND SINE OUT 1 2 3 4 5 6 7 8 9 SCHEMATIC X72 ADAPTER G P EN 390pF J2 50V MMCX 0805 LNPO Figure A 3 Edge Board Pinout Comparison X720020 54 X72 Desiger s Reference and User s Guide 097 10603 01 Rev November 2004 3 25 Inch Interface Cable 3 25 Inch Interface Cable 2 2 0 I gt 2 5 NM pl ply
27. A whichever is easiest to achieve Maximum DC undershoot must be limited to 0 5V or 10mA whichever is easiest to achieve Minimum pulse width or hold time of 50 ns 80 X72Desiger s Reference and User s Guide 097 10603 01 Rev A November 2004 72 1PPS Algorithm Operation Input impedance is gt 100K allowing the user to terminate the 1PPS at the input to the X72 with 50 at the X72 input pin or drive the X72 high impedance directly with a low impedance source such as 50 O or any ACMOS gate as long as the input voltage level at the X72 pin is met as described above a The X72 rubidium oscillator subsystem must be locked to achieve synchronization a The X72 must be set up with the proper time constant and damping factor a X72 adapter kit 106495 001 is recommended to facilitate setup PC running Microsoft Windows with terminal emulation program 57600bps 8 bits with no parity X72 1PPS Algorithm Operation There are two parameters that can be modified by the user for 1PPS synchronization using the command Damping Factor and Tau Damping factor determines the relative response time and ringing in response to each step Values should be between 0 25 and 4 Values less than 0 25 will default to 0 25 while values over 4 will default to 4 Tau or time constant expressed in seconds and determines the time constant of the PLL for following a step in phase for the reference
28. SDCP Version 3 75 of 3 2001 Loader Version 2 Mode CNN1 Flag 0004 822 Unit serial code is 0009ABOO1B h current tuning state is 6 Crystal 60000000hz ACMOS 10000000 0hz Sine 10000000 0hz Ctl Reg 029C Res temp off 1 5410 Lamp Temp off 2 1142 FC Enabled Srvc high Enter Run Mode FC Mode is enabled f gt The following is an example of the response one gets by entering the letter i to get serial number and other facts of information on the X72 r gt i X72 by Symmetricom Inc Copyright 2001 SDCP Version 3 75 of 3 2001 Loader Version 2 Mode CNN1 Flag 0004 Unit serial code is 0009AB0018 h current tuning state is 6 Crystal 3938700hz ACMOS 989680 00000000hz Sine 989680 00000000hz Ctl Reg 029C Res temp off BFC53F7D lamp temp off c0074FOE FC enabled Srvc low The following is an example of entering the letter h to get the help menu from the X72 r gt h Set FC Mode Adjust DDS Frequency delta e 11 Info show program info Display lpps Delta Reg Set lpps TIC Set Service Pin Sense Set ACMOS Output Frequency N Display Control Reg Set Control Reg Dave Tuning Data Display Health Data Exit Run Mode X tQeor FU FP Ow H o 097 10603 01 Rev November 2004 X72 Desiger s Reference and User s Guide 59 Using the Symmetricom Serial Interface Protocol The following print out shows the response to the command for
29. State Discipline Move Baseline If Necessary 9 Max Rate Is This 1 PPS Inside Window Set State To Holdover Is IDif Bounce Between 0 And 1 Initialize Base Line Refine TIC Count Tum Off 1 PPS With Estimator Lock Signal Calculate Proportional Integral Derivative Update DDS Save DDS Value Once Per Minute X72 1PPS Algorithm Theory of Operation In the Discipline State the X72 uses a PID proportional integral derivative method to steer the 1PPS output of the X72 This method means the X72 average frequency offset is close to zero You can expect to see some frequency change when recovering from holdover If at any time a 1PPS input signal is more than 330 nanoseconds from its expected value the 1PPS algorithm returns to holdover state If the input source is very stable the X72 further refines the input estimate to provide a smoother frequency output Every minute the X72 saves the DDS setting in case holdover occurs Since some receivers take a long time to produce 330 of error after signal loss the X72 reverts to the DDS value from 2 periods before the 1PPS becomes invalid 720038 Figure D 10 X72 Discipline State 097 10603 01 Rev November 2004 X72 Desiger s Reference and User s Guide 93 72 1 Algorithm Theory of Operation 94 X72 Desiger s Reference and User s Guide 097 10603 01 Rev November 2004
30. The range of Tau is 5 to 100 000 seconds Values outside this range will cause both the Damping Factor and Tau to change to the factory default settings Factory Default The factory default requires no inputs to the rubidium oscillator from the user The default value for Damping Factor is 1 and the default Tau is 400 These values are a good starting point and will work well for most GPS applications Setting the X72 for 1PPS Synchronization The following assumes the X72 has a 1PPS enabled Customer version of firmware at revision 5 02 or greater installed a Connect the X72 to the Adaptor Test Board of the Developer s Kit or to a correctly configured equivalent system See Appendix C Using the X72 Developer s Kit a Ensure the terminal emulation program is configured to 57 600 BPS 8 bits no parity no flow control and that the keyboard caps lock is off All input should be lower case 097 10603 01 Rev A November 2004 X72 Desiger s Reference and User s Guide 81 Setting the X72 for 1PPS Synchronization Apply power to the system You will see header information from the X72 displayed similar to the following where you should confirm the firmware version 7 2 by Symmetricom Inc Copyright 2004 SDCP Version 5 02 of 4 2004 Loader Version 2 Mode 1 Flag 0005 Unit serial code is 0311BB0198 h current tuning state is 6 Crystal 3938700hz ACMOS 989680 00000000hz Sine 989680 00000000hz Ctl Reg 0204 Res t
31. X72 Unit 3 25 P N 060031 001 Top View drawing not to scale DB9 connector PC COM Port Interface to HyperTerminal Program refer to Microsoft user manual 720027 Figure C 5 Developer s Kit P N 106495 001 Interconnect Diagram 74 X72 Desiger s Reference and User s Guide 097 10603 01 Rev A November 2004 X72 Development Kit Hardware Side View Interface Options edge adapter cards or cables Unpopulated LPRO Adapter Anc hored Edge Board P N 106031 XXX 2 X 8 hole connector area Edge Board Q S d 8 t LPRO Top View Filter Connector f z farside a i Filter connector provides filter 2 capacitor X72 Unit 3 Em Te 2 zZ 2 X 8 Pin Header Strip farside Standard Edge Board Test Interface Cable drawing not to scale 3 P N 060032001 Insert filter capacitor 10 MHz 390 pf NPO 5 m 13 MHz 330 pf NPO 596 15 MHz 270 pf NPO 5 Location to install 390 pf capacitor Insert 390 pf sine X72 Interface Cable 3 25 26 filter capacitor P N 060031 001 customer supplied Connector Supplied 390 pf For tests involving measurements of the Spur and Sine Amplitude Output the Symmetricom supplied 3 25 cable must be used with a customer supplied 390 pf capacitor for optimization of the signal The capacitor must be connected as shown in the diagram above This capacitor is not required for the
32. ake it possible to combine the short term with long term stability Now with X72 the solution can be even more cost effective When used with a GPS receiver the X72 provides telecommunications system performance levels that rival levels obtained using Cesium oscillators 78 X72 Desiger s Reference and User s Guide 097 10603 01 Rev November 2004 72 1PPS Functions X72 1PPS Functions The X72 can be configured to a Generate a rubidium controlled 1PPS signal Measure the difference between an incoming 1PPS signal and the X72 1PPS Synchronize the X72 s frequency and 1PPS output to the incoming 1PPS and provide very long holdover times Figure D 1 shows the X72 1PPS disciplining block diagram When an externally generated 1PPS signal is applied to pin 19 of J1 26 pin connector on a properly configured X72 the unit can provide the time interval error difference between the 1PPS input and the 1PPS generated inside the X72 see Table D 1 The difference is read using the RS232 communications j command The j command displays the difference between the 1PPS input and the 1PPS generated internally by the X72 The j command produces a number representing the number of TICS in a delta register If the X72 has a 60 MHz crystal each TIC is 16 7 ns 1 67 x E B Note that this number is in hex format A more convenient configuration is to allow the X72 to be disciplined by the incoming 1PPS signal Figure D 2 s
33. ations counters Appropriate measurement equipment can be obtained from Symmetricom Inquire with Symmetricom Marketing or your local sales representative about Symmetricom s line of test and measurement standards which includes the PRFS portable rubidium frequency standard and the FMS 2000 frequency measurement system E Note The output frequency of the X72 is more accurate than most Figure C 2 is a top view of the X72 case Figure C 3 is a diagram of the base plate showing mounting holes Table C 1 provides signal information for the J1 connector X720024 Figure C 2 Top View of X72 Case 70 X72 Desiger s Reference and User s Guide 097 10603 01 Rev A November 2004 Symmetricom Serial Interface Protocol SSIP Baseplate mounting holes 4 4X M3X 5 X 7 20 5 1 MOLEX Connector P N 52629 2651 Mate with MOLEX P N 52660 2651 shown below 01 25 3 50 89 3 250 82 6 POR m Base Plate CAUTIONS 69 9 3 00 76 The X72 is not reverse voltage protected Voltage on all input and output pins must be limited to the range specified for the X72 When designing an OEM application to use either a crystal oscillator or Bottom View Y the X72 an external series resistor may be required on pin 11 to prevent overvoltage damage 2 07 pe Dimensions in inches m
34. board pinout and layout and the 3 25 inch interface cable In This Appendix Molex Connector a Molex Connector Plug Assembly a Edge Board Pinout m 3 25 Inch Interface Cable a Edge Board Layout Drawing 097 10603 01 Rev November 2004 X72 Desiger s Reference and User s Guide 51 Molex Connector Molex Connector anoqe umoys 1592 62926 SAZIS VOISJAA IMO 20 apisu 12107 9 ON 267 08 21 011 08 2 er 00 6L 768 0222 2071 0092 201 0092 217 0021 18171 000 1992 62925 9 roo oro 001 09 912 srs 80 orz 210 oeo cer 0011 es 027 602 oost 60 008 191 OOF 196 or ve 1901 6908 OL 1 f H 9 d 3 q 2 8 Y ON 2 NOLVINHOJNI 9NIH3QHO 1 3QlS IN3NOdAOO 1G0AYV1 808 090 H EN Lnouo i 800 33S dq dAl 1 DHL unodO 20 eo Svs ime 505 oes LOL E 90 097 SS3NDIOIHL 640 TANVd Q3GN3WWOO3H A 33 7 1 33 VIO 2 ooz ONIN3dO JINYd S 0x91N 16V 950 A 7 Wiad DOS dAl 650 el et LINDUIO oor vm lt LINDO 075 050 3 o X
35. ce and User s Guide 097 10603 01 Rev November 2004 Initialization State Initialize Zero All Variables Is Coef y2 lt 10 or gt 100 000 Set To Auto Mode Set Up Time Constant And Damping Factor Set Startup Flag Set State To Holdover X720034 Figure D 6 X72 Initialize State X72 1PPS Algorithm Theory of Operation During initialization the algorithm sets up variables based on the time constant TC and damping factor DF The X72 checks for 1PPS input once per second and if present it enters the holdover state Automatic mode is used when the time constant is set to O The X72 1PPS is in the initialization state when there is no 1PPS applied The j command shows the 1PPS count 097 10603 01 Rev A November 2004 X72 Desiger s Reference and User s Guide 89 72 1 Algorithm Theory of Operation Holdover State Holdover Confirm DDS is set to value from 2 minutes before holdover adjust if not Add IDif to accumulators and increment count of data points Points gt Sample Size Set State to CalcSlope During holdover 1PPS input statistics are accumulated and periodically the results are calculated CalcSlope State The sample size is set to 120 data points 120 seconds Figure D 7 X72 Holdover State 90 X72 Desiger s Reference and User s Guide 097 10603 01 Rev November 2004 72 1 Algorithm Theory of Operat
36. ches customer s selection Host can alter during operation but host cannot alter the default power up condition 5 C field Boost 0 Low C field Controlled by firmware an automated 1 High C field function 6 SINE Output 0 Enables Output to Default is set at Factory per Configuration file Enable 40 of max output that matches customer s selection Host 1 Disables Output can disable SINE output but host cannot alter the default power up condition Note if a SINE filter is not installed SINE enable will not provide an output SINE Output Level 0 Zero Level Controlled by firmware set at factory Adjust 1 1 Adds 30 of max Output 8 SINE Output Level 0 Zero Level Controlled by firmware set at factory Adjust 2 1 Adds 20 of max Output 9 SINE Output Level 0 Zero Level Controlled by firmware set at factory Adjust 3 1 Adds 10 of max Output 10 SERVICE 0 Unit is OK Controlled by firmware Automated 1 Unit requires Service Function 11 15 Reserved Not Used user cannot set Note When altering the Control Register these bits are masked out by firmware the Host will consider these bits as DON T CARE 097 10603 01 Rev A November 2004 X72 Desiger s Reference and User s Guide 65 Using the Symmetricom Serial Interface Protocol 66 X72 Desiger s Reference and User s Guide 097 10603 01 Rev November 2004 Appendix Usin
37. d Edge Board The Standard Edge Board version PN 106569 003 is intended for implementations where the Edge Board is connected directly into the system board by soldering directly to the PCB or plugging into a socket provided by the user see example below The Edge Board achieves its mechanical stability from the direct connection P N 106569 003 2 X 8 Pin Header Strip farside X720008 Figure 2 3 Standard Edge Board The Standard Edge Board includes the following m 390 pf capacitor 10 resistor m 15 uF capacitor m Pad for coaxial connector for sine output m Soldered 2 x 8 pin connector m Adapter for connection to PCB Standard Edge Board 720009 Figure 2 4 Standard Edge Board Mounting Example 30 X72 Desiger s Reference and User s Guide 097 10603 01 Rev November 2004 Design Integration Considerations Mechanical Considerations The Anchored Edge Board The Anchored Edge Board PN 106569 002 can be used in applications where the Edge Board is not plugged into a PCB and does not have a solid electrical connection such as a soldered header that can keep the Edge Board in place in harsh vibration environments Two anchor points are provided to accommodate these applications Anchor Points X720010 Figure 2 5 Anchored Edge Board The Anchored Edge Board includes the following m 390 pf capacitor a 10 resistor m 15 uF capacitor m Pad for coaxial connector for sine output a Unpo
38. dely varying impedance at other frequencies you must take this into consideration if the X72 rf output is driving a non buffered filter Note that the X72 is specified as delivering 0 5 Vrms typical into a 50 resistance load Loads that present complex impedance or resonances affect signal amplitude The X72 can drive a properly terminated transmission line of 50 Q characteristic impedance Note A 390 pf capacitor from the 10 MHz sine output to the sine return is required within four inches of the output connector It can be located across the 50 Q terminator see Figure 2 1 If the sine output port is disabled its characteristic impedance remains the same AC Coupled RF Load The X72 is designed to tolerate an ac coupled rf load without waveform distortion provided the coupling capacitor is low impedance at 10 MHz for example a 0 01 uF capacitor has an X of 1 6 which is small compared to the 50 nominal output impedance The rf output stage of the X72 uses an ac coupled design Symmetricom recommends that you use a ceramic coupling capacitor with an X7R or NPO dielectric Transformer coupled RF Load The transformer coupled rf load is used to break up ground loops It can also be used to provide some bandpass filtering However it also attenuates the rf signal making it difficult to provide a tight tolerance on the rf output level It is also difficult to obtain an inexpensive off the shelf wide operating temperature range
39. e accuracy at shipment is lt 5 typical when power has been connected for the proper amount of time After four minutes the rubidium oscillator will reach a locked condition and its output signals will stabilize E Note Signals will appear at the outputs immediately after power is applied to the unit but these output signals will swing up to 2 6 until after the oscillator has locked After 7 5 minutes the accuracy of the X72 oscillator will be at 1xE ES Aging and temperature coefficient performance of the X72 unit will vary according to the application profile specified by the customer at time of order Refer to the X72 product specification for information on application profiles and unit performance 72 X72 Desiger s Reference and User s Guide 097 10603 01 Rev A November 2004 X72 Development Kit Hardware Performance of the unit can be monitored and certain parameters can be selectively modified through the SSIP firmware included in the unit Connect the X72 to the COM port of a PC running Windows 95 or later versions Use a terminal emulation program such as Procomm Plus by Symantec or Windows HyperTerminal The X72 communications interface is described in the following section X72 Development Kit Hardware Test Adapter Board and Edge Adapter Cards The X72 Development Kit is provided for easy lab setup to evaluate the performance and characteristics of the X72 product The development kit consists
40. e time is 4 For larger frequency change 100 lt cr gt changes repeated steps equal to or smaller than 4E should be used Unit always powers up at free running factory set frequency This command is always relative to the free running frequency h None To be Specified HELP command Displays menu i None To be Specified Outputs Unit information While dumping data clock outputs are not guaranteed to meet specifications during the use of this command 62 X72Desiger s Reference and User s Guide 097 10603 01 Rev A November 2004 Table 2 Run Mode Commands Continued User Output to X72 example of command and data to give 10 MHz for a VCXO of 60 MHz is o3 Response to Host To be Specified Using the Symmetricom Serial Interface Protocol Command Name and Description Loads the value of N to set the ACMOS output frequency N 1 65536 Output FACMOS is equal to crystal frequency divided by 2N For values outside range unit sends an illegal notice E uses the previous valid setting p None To be Specified Displays Control Register See Table B 5 q Hex data to set or reset bits To be Specified Set Control Register in the Control Register immediately follows the command example q3A Allows enabling or disabling of outputs See Table B 5 t SAVE command To be Specified Saves all changes made Example to SAVE changes NOTE if the t co
41. emp off BFC53F7D Lamp temp off C003B7E9 FC disabled Srvc low r Note It is not necessary for the X72 to be locked to enter the 1PPS configuration commands but it must be locked for actual synchronization to occur Changing the y Coefficients At the x prompt type y then 1 then Enter 1 indicates that you wish to enter the Damping Factor Enter a value between 0 25 and 4 and press Enter see Note 3 on page 84 and X72 1PPS Algorithm Operation on page 81 At the x prompt type y then 2 then Enter 2 indicates that you wish to enter the Time Constant Enter a value between 5 and 100000 and press Enter see Note 3 on page 84 and X72 1PPS Algorithm Operation on page 81 At the x prompt type z This saves the 1PPS configuration data to non volatile memory If the y coefficients are not saved with the z command the X72 reverts to the previously saved configuration upon restart The X72 responds with the following output see Note 9 on page 84 rz Saving Tdata 2 serial number xx 1PPS Coefs saved The Coefficients Factory Default If the factory default values of Damping Factor 1 and Tau 400 are acceptable for your application no modifications to the y coefficients are required The X72 1PPS disciplining is enabled at the factory allowing the unit to work right out of the box If you wish to return the y coefficients to the factory defaults enter the value 0 for both the Damping Fac
42. etermines whether the 1PPS input is useable by calculating the rate of change in timing measurements that are taken once per second Once 1PPS input is qualified the X72 1PPS algorithm determines if it is necessary to adjust the counter that produces the 1PPS output JamSynch state The algorithm then begins to adjust the output frequency of the X72 to keep the 1PPS output aligned with the 1PPs input This is the disciplining state and the control method is a Proportional Integral Derivatives PID scheme The amount of frequency change and the length of time required to reach 1PPS accuracy can be adjusted by setting y1 damping factor and y2 time constant parameters During this disciplining state the timing of each 1PPS input is compared to the expected value If the offset exceeds 333 nanoseconds the algorithm changes to the HoldOver state and the process begins again Refer to the following figures for additional details 097 10603 01 Rev A November 2004 X72 Desiger s Reference and User s Guide 87 72 1 Algorithm Theory of Operation X72 1PPS Algorithm High Level Flow Chart X72 Generated 1 PPS Arrives Get TIC Differences Between 1 PPS Output 1 PPS State Present And 1 PFS Input Dispatch Save As IDif No Hold E over JamSynch x Initialization Complete Yes Exit X72 1 PPS 720033 Figure D 5 X72 1PPS Algorithm States 88 X72 Desiger s Referen
43. ets to install and solder a 2 x 8 pin connector between the two boards The LPRO filter connector does not require the installation of a filter capacitor since it was designed to provide a filtering function 097 10603 01 Rev A November 2004 X72 Desiger s Reference and User s Guide 33 Design Integration Considerations Thermal Considerations Standard Edge Board P N 106569 003 2 X 8 hole connector area LPRO Compatible Option 2 X8 pin connector adapter X72 X72 Standard Edge Board and LPRO Connector side view Figure 2 9 Thermal Considerations 2 X 8 hole connector area LPRO Filter Connector farside P N 106734 001 Filter connector provides filter capacitor 720014 Standard Edge Board and LPRO Connector Thermal Tape In order to achieve the highest ambient operating temperature for the X72 operating base plate temperature Symmetricom recommends that the bottom base plate of the X72 have good thermal contact to the mounting surface It is also very important to maintain a uniform temperature into the base plate of the X72 through its mounting points The X72 unit operates normally without thermal tape In some field applications the tape may simplify customer system thermal design requirements N Warning To avoid personal injury attach the X72 to a heat sink to prevent it from becoming too hot to touch The X72 maximum base plate temperat
44. ference and User s Guide 25 Description Specifications 26 X72 Desiger s Reference and User s Guide 097 10603 01 Rev November 2004 Design Integration Considerations Chapter 2 Design Integration Considerations This section provides information on mounting and mating connectors operating temperature electrical interface EMI and noise susceptibility In This Chapter a Mechanical Considerations m Thermal Considerations m External Interfaces and Grounding m Electrical Interface a Frequency Control Analog Modifiable Unit Settings m X72 Susceptibility to Input Noise m X72 Reliability and Maintenance 097 10603 01 Rev A November 2004 X72 Desiger s Reference and User s Guide 27 Design Integration Considerations Mechanical Considerations Mechanical Considerations Mounting Recommendations To mount the X72 to a circuit card or chassis use the four mounting holes located at the corners of its base plate An interface cable or adapter card is required to access the X72 outputs and to interface with a host system Use four M3 stainless steel screws with a minimum penetration depth of 0 2 inch 5 08 mm and a maximum of 0 5 inch 12 7 mm to mount the unit Recommended Mating Connectors Shielded cable must be used between the X72 connector and the host system connector to meet noise and emissions requirements noted in the X72 engineering specifications It is recommend that for typical application
45. filtering is added at the input connector of the X72 it cannot have resonance points greater than the specified impedance This would result in peaking the potential for detrimental oscillations The optimum filtering is less than 1 from dc to 100 kHz In addition the input operating voltage range specified for the X72 during turn on must continue to be met during operation of the unit For example using a 1 O dc source resistance for the input supply line would not be appropriate The voltage drop resulting from this resistance caused by the turn on current or quiescent operating current would cause the input voltage to drop below the allowable value 40 X72Desiger s Reference and User s Guide 097 10603 01 Rev A November 2004 Design Integration Considerations X72 Reliability and Maintenance X72 Reliability and Maintenance Reliability The X72 is designed with a goal of twenty years of operation without retuning To accomplish this the major mechanisms impacting the need for maintenance were addressed Thus each X72 has been designed to have excess rubidium fill in the lamp to last for the required period sufficient pulling range for the voltage controlled crystal oscillator and sufficient dynamic range of the rubidium control loop Maintenance User Maintenance The X72 is considered to be factory serviceable only There is no user service adjustment or maintenance required A monitor signal is provided to allow the
46. g the X72 Developer s Kit This appendix provides information on using the Symmetricom Serial Interface protocol SSIP and includes signal information for connector J1 It also provides a developer interconnect diagram and an interface options diagram In This Appendix Introduction Symmetricom Serial Interface Protocol SSIP Start up Sequence X72 Development Kit Hardware 097 10603 01 Rev November 2004 X72 Desiger s Reference and User s Guide 67 Introduction Introduction The X72 Developer s Kit is provided by Symmetricom as a design aid and development tool It permits a design engineer to experiment with Symmetricom s X72 product in various applications and determine how to implement it in the most advantageous manner The developer s kit contains a hardcopy of this document the X72 unit a 3 foot 0 914 M interface cable the adapter board assembly application notes and a CD with electronic files documenting the specifications and performance of the unit A 90 to 264 Vac universal power supply with an IEC connector is optional and can be specified at time of order Note Users must supply a power cable to connect the adapter board to main power Users may provide their own 12 Vdc source as long as proper polarity is observed Mounting the X72 Unit The X72 is designed to mount flush onto a heat absorbing surface using the four mounting holes During demonstration testing if a heat absorbing su
47. ge the output lock indicator mode with the g command is as follows a Atthe x prompt type g then type either 0 1 or 2 depending on the desired output mode and press Enter E Notes 1 These numbers are in HEX format 2 1ppsStates 0 to 2 Initialize 3 9 Holdover 6 to 8 Disciplining 3 When connecting to a GPS receiver the factory default mode is recommended Start with y1 1 DF and Y2 400 TC in seconds These values work well for most GPS receivers Use Z command to save your settings X72 Rubidium system locks approx 5 minutes after startup X72 initial frequency must be less than 3PPB for 1PPS to lock Initial 1PPS lock occurs between 3 and 5 minutes after both lock and valid 1PPS are present Confirm the firmware version by issuing the i command xx is a value returned which is the hex equivalent of the number of times the table has been written to TData can be either 1 or 2 Table D 2 1PPS Firmware Versions Customer Standard Customer LED 5 06 5 08 84 X72 Desiger s Reference and User s Guide 097 10603 01 Rev November 2004 Flywheeling Recovery Normal Flywheeling Recovery Normal FILE NAME selected 1PPS RMS jn 5 1PPS 151 3 Plat options 500 400 1 1 1 1 200 BMS 5 200 i d 400 500 prr pir paar erem e m p
48. gnal 20 LOCK signal 36 45 69 LPRO adapter 33 magnetic fields 44 mating connectors 28 mode administrative commands 62 factory commands 62 FC 60 run commands 58 62 modulation spurs 40 mounting recommendations 28 mounting screws 68 noise 40 notes defined 14 operating temperature 19 operating voltage 40 output control register 62 output frequency 40 ACMOS 37 output signals 45 command 60 19 phase noise 40 power 68 power requirement 19 power source and current pulses 44 power supply 69 power up 44 PRFS 45 purpose of this guide 12 recommendations defined 14 related documentation 15 resistor 10 ohm 30 31 resonance points 40 rf load 36 rf output 36 RMA number 48 RS232 19 run mode commands 58 62 5 screws mounting 68 SDH 19 serial port 20 service information 41 service signal 37 shielded cable 28 signal LOCK 36 45 69 lock alarm 20 signal accuracy 45 SONET 19 spur integrity 40 SSIP 20 37 45 58 69 frequency control 38 modifying operation 39 performance monitoring 73 structure of this guide 12 Symmetricom Serial Interface Protocol see SSIP T temperature base plate 34 correction 38 limits 44 range 18 19 test board interface 73 thermal tape 34 troubleshooting 48 typical applications 19 U upgrades firmware 48 V voltage controlled crystal oscillator VCXO 36 37 47 96 X72 Desiger s Reference and User s Guide 09
49. hows the test bench setup The 1PPS disciplining mode is enabled by default It can be temporarily disabled by issuing the 9 command followed by a 1 see The g Command page 83 Typical performance data for this configuration is shown in Figure D 3 and Figure D 4 1 PPS Divider 1PPS JamSynch Rb Physics Quartz Oscillator Time Interval X72 1 PPS DS Counter Algorithm 60 MHz Divider X720029 Figure D 1 X72 Time and Frequency Control System 097 10603 01 Rev A November 2004 X72 Desiger s Reference and User s Guide 79 System Requirements GPS Antenna RS 232 PC With Terminal Emulator 1575 MHz 10 MHz GPS Receiver 1 PPS Signal x72 M n 1 PPS Out 3 3V or 5 0V 10 32 VDC Power Supply Power Supply 720030 Figure D 2 Test Bench setup System Requirements The following information lists the requirements for 1 PPS setup and operation m X72 with 1PPS output enabled GPS receiver with less than 300 ns noise a One pulse per second input signals must have repeatable rise time with minimal ringing and must conform to the following 1PPS input can be driven by a standard 3 3 volt logic 5 volt CMOS or 5 volt TTL with normal operation at Input voltage logic high 2 00V minimum Input voltage logic high 5 50V maximum Input voltage logic low 0 00V minimum Input voltage logic low 0 80V maximum Maximum DC overshoot must be limited to 5 5V or 10m
50. ides information on dimensions performance and connector pinouts In This Chapter m Overview m Typical Applications m Specifications 097 10603 01 Rev A November 2004 X72 Desiger s Reference and User s Guide 17 Description Overview Overview The X72 rubidium Rb oscillator is the newest and smallest of Symmetricom s family of precision frequency generator components This fifth generation Rb oscillator reflects significant advances in physics miniaturization and integration and offers a low height 0 70 inch 17 7 mm a small footprint and an industrial temperature range of 40 C to 85 C 720001 Figure 1 1 X72 Rubidium Oscillator Drawing on over 30 years of experience the X72 design has been refined for low cost mass production and can be easily integrated into time frequency and synchronization systems requiring only one input supply voltage It can be mounted directly onto a circuit board as a component of a module used in 0 8 inch wide card slots It offers the high reliability and accuracy of a rubidium oscillator in a new design concept benefiting from the many years of experience Symmetricom has gained in fielding tens of thousands of rubidium oscillators 720002 Figure 1 2 Size Difference of X72 top and Vintage FRK Rb Oscillator 18 X72 Desiger s Reference and User s Guide 097 10603 01 Rev A November 2004 Description Typical Applications Typical Applications The ele
51. ion Calcslope When the frequency difference between the X72 and the 1PPS source is calculated if the difference is lt 3 x E the state changes from holdover to JamSynch State CalcSlope This state executes every 120 seconds And Intercept during holdover Calculate Slope Absolute Slope Set State To lt 3E9 Holdover Save Intercept For Possible Use Later 15 Startup Flag Set Yes Set X72 Frequency Reset Startup Flag Is 1 PPS Intercept gt 1 us Set JamSynch Flag Set State To JamSynch X720036 Figure D 8 X72 Calcslope State 097 10603 01 Rev November 2004 X72 Desiger s Reference and User s Guide 91 72 1 Algorithm Theory of Operation JamSynch Figure D 9 State JamSynch JamSynch Flag Set 5 This The Second Pass Set 1 PPS Initialized PID Reset JamSynch Flag 6 Good Pulses Received Tum On 1 PPS Lock Signal X720037 When the X72 1PPS output is compared to the X72 1PPS Input if the difference is gt 1 usec the state returns to holdover to collect a second data set When two consecutive slopes are in range the X72 s 1PPS output is synchronized to its 1PPS input If the difference is lt 1 usec the algorithm waits 6 more pulses and then advances to the Discipline state X72 JamSynch State 92 X72 Desiger s Reference and User s Guide 097 10603 01 Rev November 2004 Discipline
52. ir tuning or adjustment range providing a month s warning of this situation X72 Frequency Control Signal The X72 frequency control signal is an analog input between 0 and 5 Vdc that can be enabled or disabled at the factory making it a default setting or by the customer at a later date using the SSIP The Service BIT can be selectable high or low When in use the smallest incremental frequency change is 2 12 or f 2 The unit always powers up to the preset free running factory set frequency Adjustments to the frequency are always relative to the free running frequency of the unit see also Frequency Control Analog on page 38 X72 ACMOS Output Frequency The ACMOS output frequency is equal to the crystal frequency divided by 2N Nisa number from 1 to 65536 For example the SSIP command to modify the output of the VCXO for an output of 10 MHz from a 60 MHz is 03 097 10603 01 Rev November 2004 X72 Desiger s Reference and User s Guide 37 Design Integration Considerations Frequency Control Analog Frequency Control Analog Greater Than 1xE Internal or External Control The external frequency control circuitry is designed so that with no voltage applied at J 11 the voltage will self bias to mid range or 2 5V This input can also be turned off via the SSIP to eliminate any source of noise In some versions of the X72 this function can be turned off by customer request on power up If it is to be used
53. isregard ESD cautions All ESD cautions use this symbol ESD cautions are installation operation or maintenance procedures practices conditions or statements that if not strictly observed may result in possible personal injury electrostatic discharge damage to or destruction of static sensitive components of the equipment Electrical Shock Caution To avoid electrical shock and possible personal injury do not disregard electrical shock cautions All electrical shock cautions use this symbol Electrical shock cautions are practices procedures or statements that if not strictly observed may result in possible personal injury electrical shock damage to or destruction of components of the equipment Recommendation All recommendations use this symbol Recommendations indicate manufacturer tested methods or known functionality Recommendations contain installation operation or maintenance procedures practices conditions or statements that provide important information for optimum performance results Note All notes use this symbol Notes contain installation operation or maintenance procedures practices conditions or statements that alert you to important information which may make your task easier or increase your understanding 14 X72 Desiger s Reference and User s Guide 097 10603 01 Rev November 2004 Related Documents and Information Related Documents and Information See your Symmetricom
54. later it must be enabled through the SSIP refer to Appendix B Symmetricom Serial Interface Protocol Time Response of External Frequency Control The external analog frequency control is a sampled input with a typical response time constant of 154 ms Temperature Compensation of Frequency One of the key specifications for an atomic frequency standard is the temperature coefficient The X72 is designed for a low temperature coefficient without the need for temperature correction However if the application requires a tighter temperature coefficient and a more automated temperature compensated unit was not ordered you can monitor the base plate temperature of the X72 and apply a correction signal via the External frequency control pin or through the SSIP A production calibration run is required to set the X72 temperature at several points and determine the correction summary This method can be successfully used for moderate correction for example to bring the maximum frequency change over the full operating temperature range to less than 1 0 Compensation using this scheme is generally suitable only for steady state conditions Inherent mismatches between the thermal time constants of the mechanisms that cause temperature coefficient errors thermal time constant of the monitoring circuitry and transients from time constant mismatches will occur These transients are minimized if temperature ramp rates are limited Changing les
55. llows you to change the X72 to operate in any of three modes which affect the output of the Lock Pin pin 21 Note that this 1PPS mode can be changed by the user but cannot be saved If power is cycled to the unit it reverts to the factory default The modes are 0 1 Disciplining Disabled Normal Rb Lock Pin functionality Only the Rb loop needs to be locked to indicate a locked condition on pin 21 1 1PPS Disciplining Enabled Normal Lock Pin functionality Only the Rb loop needs to be locked to indicate a locked condition on pin 21 2 1PPS Disciplining Enabled Requires both Rb loop to be locked AND 1PPS synchronization lock to indicate a locked condition on pin 21 097 10603 01 Rev November 2004 X72 Desiger s Reference and User s Guide 83 Setting the X72 for 1PPS Synchronization Note that there are two types of 1PPS Customer firmware The 7PPS Standard firmware provides an Rb or Rb 1PPS lock indicator at 21 and a Service indicator on pin 8 of the X72 I O connector The 1PPS LED firmware uses the same functions for pin 21 but pin 8 is reserved for 1PPS lock indication only There is no Service pin on the 7PPS LED versions The factory default mode set by the command for each firmware version is m 1PPS Standard Firmware Mode 2 Rb lock and 1PPS lock indicated on pin 21 a 1PPS LED Firmware Mode 1 Rb lock only indicated on pin 21 and 1PPS lock indicated on pin 8 The key sequence to chan
56. logy has made possible time and frequency synchronization world wide Connecting the 1PPS output from a commercial civilian GPS receiver to an X72 provides a cost effective system that maintains highly accurate time and frequency even when GPS signals become unavailable for example jamming and during antenna maintenance The GPS system provides worldwide 1PPS signals with extremely good long term stability i e lt 1 x E averaged over 24 hours However the short term stability of this signal is often compromised by various noise sources for example man made atmospheric conditions crosstalk RF multi path or inter symbol interference and GPS receiver oscillator limitations Symmetricom has pioneered the use of rubidium oscillators in telecommunications applications Telecommunications applications often require long term and short term stability beyond the range of free running quartz oscillators For example cellular CDMA systems often require 1PPS signals to be synchronized within 2 us over very long periods of time even when GPS signals are not available To achieve this performance system designers must combine the benefits of short term stability from a rubidium or low noise OCXO with long term stability from GPS Loran C Glonass or Cesium Symmetricom is the leader in system products with microprocessor driven circuitry that uses the GPS 1PPS system to steer various oscillators Cesium Rubidium and Quartz These products m
57. m Front View 2 0 42 10 7 720025 Figure 3 X72 Dimensions Table C 1 Connector J1 Signal Information SIGNAL 1 PIN NAME TYPE SIGNAL FUNCTION 1 7 VDD bundled PWR Power input 8 SERVICE Output Service required within 30 days based on unit health 9 DOUT Output UART data out ACMOS logic level 10 DIN Input UART data in to oscillator 11 FREQ CTRL Analog Frequency control analog input between 0 and 5 Vdc 12 18 VSS bundled GND Power amp signal return 19 1 PPS IN Input 1 PPS input positive edge triggered 20 1 PPS OUT Output 1 PPS output may be enabled disabled digitally 097 10603 01 Rev November 2004 X72 Desiger s Reference and User s Guide 71 Start up Sequence Table C 1 Connector J1 Signal Information Continued SIGNAL PIN NAME SIGNAL FUNCTION 21 LOCK Output If low indicates Rb osc is locked 22 FXO Output FXO ACMOS output equalling the VCXO frequency 23 FACMOS RTN GND Return for FACMOS amp FXO signals 24 FACMOS OUT Output FACMOS ACMOS Output Option equals VCXO frequency divided by 2xN N is selectable 25 FSINE RTN GND Chassis ground return signal for FSINE signal 26 FSINE OUT Output FSINE Sine output option equals VCXO frequency Note 1 All inputs and outputs are ESD protected 2 High impedance Note Refer to Appendix A for the listed connector manufacturer s specification sheets Start up Sequence Th
58. mmand is not used 5987717 lt cr gt unit defaults to factory settings at next power up To be Specified Displays Health Monitor data Table B 3 Factory Mode Commands User Output to X72 Response to Host command Name and Description Command DATA a None a gt Goes to Administration mode i None Outputs 6 lines of Banner same Displays Unit Information as power up information r Run Mode Enter RUN mode FC mode is Goes to RUN mode disabled enabled operating mode Note This mode and ADMIN mode allow the loading of new code or updates or reconfiguring defaults in the field It is not a normal 097 10603 01 Rev November 2004 X72 Desiger s Reference and User s Guide 63 Using the Symmetricom Serial Interface Protocol Table B 4 Administrative Mode Commands User Output to X72 Response to Host Command Name and Description Command DATA a None Outputs 6 lines of Unit Information Same as the i banner same as command in FACTORY mode and power up RUN mode b File from To be Specified Operating this command without valid Symmetricom file will not overwrite the existing self burning data stored in FLASH memory None x f gt EXIT Administrative mode to FACTORY mode y None Y asks are you sure Soft reset Restarts processor 2 None Z asks are you sure Puts unit into a mode where it will wake only when the power is recycled
59. n e he Eae d re e 75 X72 Time and Frequency Control 79 Test Bench SBIUD 80 Flywheeling Recover with 1PPS offset lt 1usec 85 Flywheeling Recover with 1PPS offset gt 1usec 86 X72 IPPS Algorithm iOS eee eee ee 88 X72 nitiali e State J55 aso e cL 89 X72 Holdover State uua ius aues oae Mese Rd f eat ea Dire ACH d Cs 90 097 10603 01 Rev A November 2004 X72 Desiger s Reference and User s Guide 7 0 8 A12 CaleslOpe 91 0 9 JAMSYNCN Stale 92 0 10 X72 Discipline 5 93 8 X72 Desiger s Reference and User s Guide 097 10603 01 Rev November 2004 Tables 1 2 3 2 1 2 2 B 1 B 2 B 3 B 4 B 5 C 1 D 1 D 2 X72 Design Absolute Maximum 22 X72 Design Absolute Maximum Ratings 23 X72 Design Operating 24 Hardware Selectable lt 39 Software Selectable Items 2 ee ee ee ee n 39 Floating Point Number Representation for SSIP 61 Run Mode Commands y RE ERE Se 62 Factory Mode 63 Administrative Mode
60. npopulated Edge Board eae ety 29 Standard Edge 30 Standard Edge Board Mounting Example 30 Anchored Edge 31 Anchored Edge Board Mounting 32 3 25 Inch Connector and 32 3 25 Inch Connector Mounting Example 33 Standard Edge Board and 34 Suggested Connections for X72 Initial 44 Sequence of Start up 5 46 X72 Rb Control Loop Block 47 Molex dou Se 52 Molex Connector Plug 53 Edge Board Pinout Comparison 54 3 25 Inch Interface Cable Connections 55 Layout Drawing for Edge 56 Suggested X72 Test 69 Top View of X72 Case 70 XT2 DIMENSIONS 45 25 eS mera ne Etsi 71 Top View of X72 Test Interface Board 73 Developer s Kit P N 106495 001 Interconnect Diagram 74 X72 Interface Options 21 s EA e
61. om Serial Interface Protocol SSIP permits external communication with the X72 through the serial port connector J1 when the unit is connected to a host PC All developer mode commands a single ASCII letter and require no termination Of the eight RUN MODE commands three require the host to supply data Host Terminal Emulator Setup Set up the comm port of the PC with the following configuration a Data rate baud or B P S baud rate of the X72 is 57 6K m No parity m 8 data bits m 1 stop bit a No local echo unit echoes m No hardware or software flow control Note The X72 s UART connections are based on 5 logic levels However the Developer s Kit contains a TTL to RS232 converter that allows interfacing to a PC Data Format Run Mode Data Format Customer Mode X72 outputs are all decimal data as ASCII Coded Hex except for echoed characters Do not convert data to decimal when transmitting to the X72 All data are sent to the X72 and received back as ASCII Coded Hex The following example shows how data are encoded E Note Flow control is not permitted in Run Mode Data sent to the X72 in run mode should not be encoded 58 X72 Desiger s Reference and User s Guide 097 10603 01 Rev A November 2004 Using the Symmetricom Serial Interface Protocol The following is an example of output from the X72 after power is applied to the unit X72 by Symmetricom Inc Copyright 2001
62. on n n pan pe nnn p n pan n na pa n n pna n pre n po n pin 0 0 1 0 2 0 3 0 4 0 5 0 5 0 7 0 8 0 9 0 10 0 11 0 12 0 13 0 14 014 5 PPS seconds sample nS 132 4 eet sel REMOVE CONSTANT pras WINDOW SIZE 20 0 one pa pz BH a i MINUTES w f both PPS amp dat bie aeo e e ata Plot options Lo LU FREQ OFFSET 2 0 10 df f 2 0E 10 ooo PSI 0 0 1 0 2 0 3 0 4 0 5 0 5 0 7 0 8 0 9 0 10 0 11 0 12 0 13 0 14 014 5 seconds sample Records ofditfRecords 89 F ifNOPPSdata USE WINDOWS SHOW FOR OPERATING INSTRUCTIONS 27059 27059 594 05 720031 Figure D 3 Flywheeling Recover with 1PPS offset lt 1 In this test the X72 was synchronized to 1PPS before this data set Antenna is removed at hour 0 and reapplied at approximately hour 12 5 The X72 1PPS output signal had reached an offset of 220 nanoseconds The subsequent frequency change is what returns the 1PPS offset to 0 nanoseconds 097 10603 01 Rev November 2004 X72 Desiger s Reference and User s Guide 85 Recovery with JamSynch Recovery with JamSynch FILE selected 1 5 RMS make 8807 5 1PPS 1 23 Plot options gt t 1500 1000 RMS en e 71500
63. ontroller through a serial port connection This allows precise frequency control the dynamic frequency selection the ability to enable and disable outputs to query the system s health and acquire information about the unit s serial number operating temperature fault history initiate a self test and other performance indicators The protocol used is Symmetricom s proprietary Symmetricom Serial Interface Protocol or SSIP The simplified block diagram below shows the importance of the digital control in the unit how it controls and monitors all aspects of operation such as the heater circuits of the physics package as well as the selection of outputs 1 PPS IN E 1 PPS OUT out Xn Mod Synth XO Sil Field Status Serial Analo Contro DC DC X72 Block Diagram Conditioned Converter 10 32 Voltages EF 1 19 00 720003 Figure 1 3 X72 Rubidium oscillator simplified block diagram 20 X72 Desiger s Reference and User s Guide 097 10603 01 Rev November 2004 Description Specifications Specifications Baseplate mounting holes 4 4X 5 X 20 5 1 350 89 ___ gt
64. pulated 16 pin header strip for customer integration 097 10603 01 Rev November 2004 X72 Desiger s Reference and User s Guide 31 Design Integration Considerations Mechanical Considerations Anchored Edge Board 720011 Figure 2 6 Anchored Edge Board Mounting Example 3 25 Connector The 3 25 inch connector PN 060031 001 is an all in one connection option that includes the mating connector to the X72 and a 24 pin header that can be mounted directly on a system board The flexible cabling allows the header to be installed in various orientations to the unit 3 25 inch Connector 2 X 12 Pin Header Strip 3 25 inch Interface Cable P N 060031 001 X720012 Figure 2 7 3 25 Inch Connector and Header 32 X72 Desiger s Reference and User s Guide 097 10603 01 Rev A November 2004 Design Integration Considerations Mechanical Considerations 3 25 Connector Mounting Example Jd X720013 Figure 2 8 3 25 Inch Connector Mounting Example X72 LPRO Adapter The X72 LPRO Adapter PN 106734 001 was developed for existing Symmetricom LPRO customers The Symmetricom LPRO Low Profile Rubidium Oscillator is the most widely produced rubidium oscillator in the world and has been designed into hundreds of applications The X72 LPRO Adapter allows these customers to upgrade to the X72 without changing the physical interface in their unit The Standard Edge Board and the LPRO Compatible Option Board both have Sock
65. quence of Start up Events Note The Service signal can be Active High or Active Low depending on the unit configuration 46 X72 Desiger s Reference and User s Guide 097 10603 01 Rev November 2004 Installation and Operation Theory of Operation Theory of Operation PHYSICS Rb DISCRIMINATOR 6 8346875GHz Bis SERVO f RUBIDIUM PHYSICS PACKAGE tee es The Model X72 makes use of the atomic resonance property of rubidium Rb to control the frequency of a quartz crystal oscillator via a frequency locked loop FLL The FLL function block is shown in Figure 3 3 A microwave signal is derived from a voltage controlled crystal oscillator VCXO and applied to the 87Rb vapor within a glass cell The light of a rubidium lamp also passes through this cell and illuminates a photo detector When the frequency of the applied rf signal corresponds to the frequency of the ground state hyperfine transition of the 87Rb atom an ultra stable high Q rubidium atomic resonance light is absorbed causing a change decrease in photo detector current lpp As the change in current is small modulation techniques are required to be able to extract the desired signal out of the noise background The photo detector current is used to generate a control signal with phase and amplitude information which permits continuous regulation of the VCXO frequency The servo section converts the photo detector cu
66. representative or sales office for a complete list of available documentation knowledge of the X72 Rubidium Oscillator Contact your local representative or sales office for a complete list of courses and outlines E Note Symmetricom offers training courses designed to enhance your Where to Find Answers to Product and Document Questions For additional information about the products described in this guide please contact your Symmetricom representative or your local sales office You can also contact us on the web at www symmetricom com What s New In This Guide This revision of this guide has a new format and typography to make the text easier to read The following changes where also incorporated Removed 5 volt option information throughout manual Updated FACMOS OUT signal function information in Table 1 1 and Table C 1 Updated information in Table 1 3 Added the t command Save Tuning Data to Table B 2 Updated SSIP control register information Updated the description for the f command Adjust Frequency to Table B 2 Added Appendix D One Pulse Per Second Source Connection 097 10603 01 Rev A November 2004 X72 Desiger s Reference and User s Guide 15 What s New In This Guide 16 X72 Desiger s Reference and User s Guide 097 10603 01 Rev A November 2004 Description Chapter 1 Description This section contains a description of the X72 and lists its typical applications It prov
67. rface is not available a suitable heat sink can be ordered as an option 3 mm in size with 0 5 mm thread pitch They should penetrate no E Note The mounting screws for the X72 are metric not SAE and are more than 5 0 mm into the X72 base plate Interface Cabling Circuit Cards The X72 cable is a shielded multi conductor 26 wires cable 3 feet 0 914 M long with molex connectors at each end Adapter cards are available in 3 5 inch 8 89 cm and 1 740 inch 4 42 cm lengths A 3 25 inch 8 25 cm cable is also available Connectors The unit Molex connector is a 52629 2651 1 00 mm 0 039 pitch shielded receptacle right angle SMT connector The mating connector is a Molex 52660 plug assembly Power E Note The X72 provided in the Developer s Kit operates on 10 to 32 Vdc 68 X72 Desiger s Reference and User s Guide 097 10603 01 Rev November 2004 Symmetricom Serial Interface Protocol SSIP The X72 unit included in the kit is configured at the factory to operate at 10 to 32 Vdc If the X72 is used without the adapter board a 50 Q load is required and a 390 pf filter capacitor is recommended to prevent spurs Additional information on power requirements and precautions can be found in Electrical Interface on page 36 Symmetricom Serial Interface Protocol SSIP Setting up and interacting with the X72 unit using SSIP is covered in Appendix B Symmetricom Serial Interface Protocol Turn on Procedure
68. rrent into a voltage then amplifies demodulates and integrates it for high dc servo loop gain LOCK IN AMPLIFIER SYNTHESIZER Frequency Out GENERATOR fuop MICROWAVE GENERATOR X720017 Figure 3 3 X72 Rb Control Loop Block Diagram 097 10603 01 Rev A November 2004 X72 Desiger s Reference and User s Guide 47 Installation and Operation Troubleshooting Troubleshooting After installation if the X72 unit fails to provide outputs or the rubidium oscillator fails to achieve lock check the following a The external power supply is providing power a The external power supply is providing the correct power The interface cable may be defective perform a continuity check Note All pins must have a connection in the cable s Molex connectors This is especially important in the case of the power and ground pins ls there excess humidity or moisture inside the operating area a ls the ambient temperature below 40 C or above 85 the unit will not startup properly in excessively cold or hot temperatures Repairs The X72 is not field repairable but some firmware upgrades can be done in the field as noted in Start up Sequence on page 45 If the unit should fail do not remove the cover of the unit and attempt to make repairs Note Unit warranty is void if the cover is removed or if the protective seals covering the two tuning and adjustment holes are torn or
69. s required mating connectors and unit operation Who Should Read This Guide This document is intended for engineers and telecommunications professionals who are designing installing operating or maintaining time frequency and synchronization systems having a requirement for a low profile and highly precise frequency generator To use this document effectively you should have a good understanding of digital telecommunications technologies and analog frequency generation and synthesis techniques Structure of This Guide This guide contains the following sections Chapter Title Description Chapter 1 Description This section contains a description of the X72 and lists its typical applications It provides information on dimensions performance and connector pinouts Chapter 2 Design Integration Considerations This section contains mechanical issues pertaining to X72 mounting and mating recommendations including thermal and EMI considerations external interfaces and grounding frequency control susceptibility to noise and reliability goal Chapter 3 Installation and Operation This section contains the information necessary to properly install and operate the X72 unit including a simplified theory of operation and maintenance and warranty Appendix A X72 J1 Connector and Plug This appendix identifies the Molex J1 connector and its mating plug and provides pinout information for
70. s than 2 C minute base plate temperature should result in negligible transients from mismatches 38 X72 Desiger s Reference and User s Guide 097 10603 01 Rev November 2004 Design Integration Considerations Modifiable Unit Settings Modifiable Unit Settings You can modify some features of the X72 operation are modifiable by the customer Refer to the X72 Developer s Kit document DK 106031 for information on how to use the SSIP to use these functions E Note You cannot alter the default power up conditions Table 2 1 Hardware Selectable Items Item Action FXO Enable Turn the XO frequency output on or off 1PPS Output Enable Turn 1PPS output on or off ACMOS Output Enable Turn the ACMOS output on or off Sine Output Enable Turn the sine outputs on or off Table 2 2 Software Selectable Items Item Action Analog Frequency Adjust Enable or disable frequency control function Adjust Frequency Adjust output frequency from the factory preset value HELP Displays the HELP menu Change ACMOS output Defining N sets the ACMOS output frequency frequency divider View Control Register Displays current settings of the control register Set Control Register Enable or disable outputs View Unit Information Displays X72 information stored in firmware View Health Monitor Data Displays history file of error or fault information Note 1 Minimum frequency change is 2 12 or
71. s this interface cable be no longer than 4 inches 10 cm Side View Interface Options edge adapter cards or cables Unpopulated P N 106031 XXX oo CERE LPRO Adapter 2X8 hole connector area Top View P N 106568 001 P N 106734 001 Filter connector provides filter capacitor 3 25 Connector X72 Unit 2 X 12 Pin Header Strip P N 106569 003 3 25 P N 060031 001 Interface cable 2X8 Pin Header Strip farside Standard drawing not to scale Edge Board Test terface Insert filter capacitor 10 MHz 390 pf NPO 5 13 MHz 330 pf NPO 5 15 MHz 270 pf NPO 5 720006 Figure 2 1 Adapter Cards Cables and Options 28 X72 Desiger s Reference and User s Guide 097 10603 01 Rev November 2004 Design Integration Considerations Mechanical Considerations Integrating the X72 into a System Symmetricom has developed several integration options to aid the system designer in integrating the X72 into their application These options provide a variety of connection schemes Each option is described below Unpopulated Edge Board The Unpopulated Edge Board is a small printed circuit board PCB that plugs directly into the X72 s Molex connector The Unpopulated Edge Board includes unpopulated pads for the following components 16 pin header See pin out comparison in Appendix A X72 J1 Connector and Plug a Coaxial connector for the Sine Output m Resi
72. screen A command you enter at a system prompt or text you r gt w r a enter in response to a program prompt You must enter commands for case sensitive operating systems exactly as shown Lock in A word or term being emphasized Symmetricom does not recommend A word or term given special emphasis 097 10603 01 Rev A November 2004 X72 Desiger s Reference and User s Guide 13 Warnings Cautions Recommendations and Notes Warnings Cautions Recommendations and Notes Warnings Cautions Recommendations and Notes attract attention to essential or critical information in this guide The types of information included in each are explained in the following examples N Warning To avoid serious personal injury or death do not disregard warnings All warnings use this symbol Warnings are installation operation or maintenance procedures practices or statements that if not strictly observed may result in serious personal injury or even death Caution To avoid personal injury do not disregard cautions cautions use this symbol Cautions are installation operation or maintenance procedures practices conditions or statements that if not strictly observed may result in damage to or destruction of the equipment Cautions are also used to indicate a long term health hazard ESD Caution To avoid personal injury and electrostatic discharge ESD damage to equipment do not d
73. st as es nd SS oe 83 Flywheeling Recovery 85 Recovery with 0 5 86 X72 1PPS Algorithm Theory of Operation 87 X72 1PPS Algorithm High Level Flow 88 initialization ct Sth ek Hd A ad 89 BIN SG Skea 90 Sim af Ea rial oe ak 6S 91 AMIS VINCI hee a pa e mue yee es aeu 92 DISCIDIIIB Motor tibt n Pee a Ud ND I PAR ded BS 93 097 10603 01 Rev A November 2004 X72 Desiger s Reference and User s Guide 5 6 X72 Desiger s Reference and User s Guide 097 10603 01 Rev November 2004 Figures 2 4 2 6 2 7 2 8 2 9 3 1 3 2 3 3 A 1 A 2 A 3 A 4 A 5 C 1 C 2 C 3 C 4 C 5 C 6 D 1 D 2 D 3 D 4 D 5 D 6 D 7 X72 Rubidium Oscillator RU CR 18 Size Difference of X72 top and Vintage FRK Rb 18 X72 Rubidium oscillator simplified block diagram 20 X72 Dimensions and Connector Pin Assignments 21 Total X72 Quiescent Power Dissipation Typical free convection 25 Representative X 72 f f versus Temperature uncompensated 25 Adapter Cards Cables and 28 U
74. stor and Capacitor pads to allow for improved Sine Output dc filtering See Electrical Interface on page 36 From the various interface points on the Edge Board a system designer can access all inputs and outputs of the X72 and can mount the connectors that are necessary for their application This provides a variety of connection schemes The examples included in this document are just a few of the integration methods possible with these edge boards The Edge Board comes in three different versions Unpopulated PN 106568 001 Standard PN 106569 003 and Anchored PN 106569 002 The three versions are electrically identical The Anchored version is 3 5 inches 8 89 cm long The Standard and Unpopulated versions are 1 74 inches 4 42 cm long Each card has two anchor points refer to Figure 2 2 Figure 2 3 and Figure 2 5 In addition the standard edge board includes the header that is mounted directly to the PCB by direct solder connection or by plugging into a socket provided by the user Refer to Figure A 3 in Appendix A X72 J1 Connector and Plug for a schematic of the connector pinouts Unpopulated Edge Board P N 106568 001 Insert filter capacitor 10 MHz 390 pf NPO 5 13 MHz 330 pf NPO 5 15 MHz 270 pf NPO 5 720007 Figure 2 2 Unpopulated Edge Board 097 10603 01 Rev November 2004 X72 Desiger s Reference and User s Guide 29 Design Integration Considerations Mechanical Considerations Standar
75. t DIN 0 0 8 V voltage 1PPSIN 0 0 8 High level output DOUT Service Lock 3 3 V voltage IOH 0 33 mA O mA FXO FACMOS 3 5 1PPSOUT IOH 3 5 VoL Low level output DOUT Service Lock 0 4 V voltage IOL 0 1 mA FXO FACMOS 0 4 1PPSOUT IOL 1 7ma Analog Inputs Outputs Vrc Frequency control Range of 1 5 9 with 9 V input voltage range resolution of 2 0xE Pso FSINE output power Factory set with 7 0 5 0 min dBm range Output load of 390pF 8 0 max amp 50 resistor within 4 inches of Spe FSINE pin Frequency Control AF FR Control Range Analog freq ctrl pin 1 5xE 1 5 2 2 Digital Interface 1 0 6 1 0 6 AF FREs Frequency Control Resolution 2 04 E 2AHz Hz 24 X72Desiger s Reference and User s Guide 097 10603 01 Rev A November 2004 Description Specifications 40 30 20 10 0 10 20 25 30 40 50 60 70 80 85 a e POWER DISSIPATION WATTS BASEPLATE TEMPERATURE 720005 Figure 1 5 Total X72 Quiescent Power Dissipation Typical free convection To be added when available Base plate Temperature C Figure 1 6 Representative X 72 f f versus Temperature uncompensated Note Refer to the X72 Performance Characteristics document for more detailed information 097 10603 01 Rev November 2004 X72 Desiger s Re
76. t Number 61 Appendix Using the X72 Developer s Kit Ks 68 Mounting the Unlt scat ad oe ERES Exe whee eee eee 68 Interface Cabling Circuit 68 Symmetricom Serial Interface Protocol 53 69 T r on Procedure 69 Sequelj6B 72 4 X72 Desiger s Reference and User s Guide 097 10603 01 Rev November 2004 X72 Development Kit Hardware 73 Test Adapter Board and Edge Adapter Cards 73 Appendix D One Pulse Per Second Source Connection Connection 78 Background Festa ind dii 78 KE2 IPPS FUNCIONS daga ote BS eee a ines Bee 79 System Requirements e eee 80 X72 1PPS Algorithm 81 Factory Default 9 3 PSO Ere e AEE Be EP epis 81 Setting the X72 for 1PPS Synchronization 81 Changing the y Coefficients 2 5020608 es 82 The y Coefficients Factory 82 Thei Gommand icd Lune 83 The g Command ea fu ena ho
77. ting connector and could cause intermittent loss of signals The X72 is shipped in a dust protected ESD resistant bag All connectors on any product must be suitably protected before mating in a dust controlled environment External Interfaces and Grounding Figure 2 1 shows the interface circuitry for J1 the X72 connector All signals including power power return rf output signal chassis ground and monitor lines are routed through this connector All voltage supply and ground lines must be connected at the mating connector for the X72 unit to operate properly The X72 is constructed with the chassis unit cover and signal grounds tied together at multiple points and with the power supply return isolated from both chassis and signal grounds only by a ferrite bead This robust grounding approach allows for ESD protection and low spurious emissions But it can also lead to ground loop issues for the user Workarounds commonly used to break dc ground loops at a higher level of integration are to use an rf isolation transformer for the sine rf output and or float the transformer secondary winding of the user s power supply 097 10603 01 Rev A November 2004 X72 Desiger s Reference and User s Guide 35 Design Integration Considerations Electrical Interface Electrical Interface X72 RF Outputs RF Output Impedance versus Frequency The active rf output impedance for the X72 is a nominal 50 at 10 MHz but is a wi
78. tor and Tau using the process described in Changing the y Coefficients on page 82 This causes the X72 to operate at the factory default Damping Factor of 1 and Tau of 400 82 X72Desiger s Reference and User s Guide 097 10603 01 Rev A November 2004 Setting the X72 for 1PPS Synchronization The j Command Press the j key at any time to return the current value in hex format from the Delta Register see Note 1 on page 84 as well as the 1PPS state see Note 2 on page 84 below and the following table The output format appears similar to the following r j Delta Reg 39386F5 lppsState 6 Table D 1 1PPS States Returned with the j Command Description Action Being Performed INITIALIZEOSTATE 0 Start up initialization INITIALIZE1STATE 1 Start up initialization INITIALIZE2STATE 2 Start up initialization HOLDOVERSTATE 3 Seeking usable 1PPS JAMSYNC1STATE 4 Synch X72 output 1PPS to input JAMSYNC2STATE 5 Synch X72 output 1PPS to input DISCIPLINESTATE 6 Keep X72 output 1PPS aligned to input by controlling X72 frequency PIDCALCSTATE 7 Calculations for disciplining algorithm PDATEDDSSTATE 8 Update X72 DDS based on PIDCALCSTATE output ALCSLOPESTATE 9 Calculate slope of incoming 1PPS vs X72 1PPS during holdover See X72 1PPS Algorithm Theory of Operation on page 87 for additional information on 1PPS states The g Command The g command a
79. ure described in the specifications is based on a unit covered on five sides with one inch foam to simulate free convection in air with the heat sink base plate exposed to forced air If there is air flow over the unit s top cover the X72 s maximum operating base plate temperature increases by 1 or 2 C and its power consumption at a given base plate temperature also increases by a few tens of milliwatts 34 X72 Desiger s Reference and User s Guide 097 10603 01 Rev A November 2004 Design Integration Considerations External Interfaces and Grounding As the base plate temperature continues to increase the unit eventually loses lock Above a base plate temperature of 85 C the resonator or lamp heaters shut down as control point temperatures are exceeded and the unit temperature coefficients increase to approximately 6 Water Condensation and Excessive Humidity Condensation of moisture from the air onto electrical components produces frequency spikes or instability until the heat of the operating unit drives out the water vapor Condensation will not cause a problem for environments meeting the X72 specification if the X72 base plate thermal ramp rates are controlled so that they rise at less than 2 C minute Excessive Dust Operating the unit in dusty conditions may cause unexpected thermal effects if dust builds up on the top surface Excessive dust will also contribute to contamination in the shell of the ma
80. vated operating temperature range of the X72 sets a new high point for this type of atomic reference Compared with traditional quartz oscillators the stability of the X72 allows it to maintain excellent frequency control even when the operating temperature goes above 85 C Even if the host system overheats in fault mode the X72 oscillator continues to produce a stable and accurate time or frequency reference The X72 is easily integrated into time and frequency systems because of its low profile The height and footprint are designed to accommodate 0 8 inch 4 1 wide card slot applications The unit operates with a low power requirement between 10 and 32 Vdc This design is being successfully applied as an OEM component in wireless telecom networks such as digital cellular PCS base stations SONET SDH digital network timing etc Linked with a GPS receiver or other external timing reference the X72 provides the necessary timing requirements for CDMA cellular and PCS systems The low temperature coefficient and excellent frequency stability extend holdover performance when the GPS signal is not available Temperature compensated units are available for those special applications requiring even better temperature performance The X72 s 20 year stability without the need for retuning permits extended operating periods without maintenance long life Rb lamp extended crystal control range The design produces a stable frequency with good short
81. w for X72 Health Data wellness r gt w AData SCont 6012 SerNum 18C PwrTicks LHHrs 17 Ticks Hrs 17 Ticks lt trVolt LVthermC RVthermC Qut MVoutC dTempLo dTempHi dVoltLo dVoltHi iFpgaCtl dCurTemp dLVoutC dRVoutC dmv2 demAvg LE Gl 8 4 4 3 3 PwrHrs 18A 11A6848 3D2E3 P17 41883621 P5 40A158E9 41381AF5 Lmp 3FAA43C6 Res 3FA10F45 39500000 B9DD8000 LVolt 3F327288 94005E0 00000000 42928000 134DC6A 41C1CA16 029 42690000 258538 E19A67 F 3F337D72 The following print out shows how entering the letter followed by an integer sets the enable disable feature of FC mode Integer zero followed by lt cr gt disables FC mode and any nonzero integer followed by lt cr gt enables the FC mode r gt a lt nonzero integer gt lt cr gt FC mode enabled r gt a o lt cr gt FC mode disabled The following print out shows the control register contents by entering the letter p r gt p Control Reg 0291 GI 60 X72 Desiger s Reference and User s Guide 097 10603 01 Rev November 2004 Using the Symmetricom Serial Interface Protocol Factory Mode Data output from the X72 in factory mode is not intended for users outside the factory and is not described in this document be
82. wer 17 Watts Po Max quiescent power 40 C base plate 15 Watts 25 C base plate 10 Watts 85 C base plate 5 0 Watts twu Maximum warm up time 40 base plate Lock 8 Minutes to lt 1xE 25 C base plate Lock to lt 4 Minutes lt 1 9 Maximum absolute Conditions still air 45 to 85 C operating base plate convection no heat temperature sink on unit TMTBP Maximum absolute turn on Conditions still air 40 to 85 C base plate temperature convection no heat sink on unit TsTG MaxiMum Storage Temperature 55 to 85 C Maximum vibration Sine 1 inch DA or 10G 0 to 300 Hz powered but not locked Maximum vibration Sine 1 inch DA or 10G 0 to 100 Hz powered and maintaining lock Maximum altitude With respect to sea level 30 000 Feet powered up unit Maximum altitude With respect to sea level 50 000 Feet unpowered Note All outputs are short circuit protected 097 10603 01 Rev November 2004 X72 Desiger s Reference and User s Guide 23 Description Specifications Table 1 3 X72 Design Operating Characteristics 40 C to 85 C Characteristic Base plate F Symbol Unit in ambient still air convection Min Typ gnit Max Digital Inputs Outputs Vcc Supply relative to 10 to 32 volt unit 10 32 V ground Vin High level input DIN 2 5 5 5 V voltage 1PPSIN 1 8 5 5 Vi Low level inpu
83. yond Table B 1 Caution Using factory mode can result in the erasure of firmware on the X72 rendering it inoperable and making it necessary to return the unit to the factory for re programming Floating Point Number Representation The host PC must convert Floating Point numbers output by the X72 to the host s own floating point using the definition shown in Table B 1 Likewise the host s floating point numbers must be converted to X72 coding before being sent to the X72 Table B 1 Floating Point Number Representation for SSIP Floating Point Format Single Precision 31 30 29 28 127 26 25 24 23 22 21 20 19 18 17 16 E7 E5 4 E2 1 22 21 M20 M19 M18 M17 16 15 14 113 112 111 10 9 8 7 6 5 4 3 2 1 0 M15 M14 M13 M12 M11 M10 M9 M8 M7 M6 5 M4 M2 M1 Single precision floating point format is a 32 bit format consisting of a 1 bit sign field an 8 bit exponent field and a 23 bit mantissa field The fields are defined as follows Sign S 0 positive values 1 negative value Exponent lt E7 E0 gt offset binary format 00 special cases i e zero 01 exponent value 127 126 FE exponent value 127 127 FF 7 special cases not implemented Mantissa lt 22 gt fractional magnitude format with implied 1 1 M22M21 1 Range 1 9999998 127 to 1 0000000 e 126 1 0000000

X72 Rubidium Oscillator

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