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GLAST Large Area Telescope: Electronics, Data Acquisition & Flight Software TEM Power Supply

Gamma-ray Large Area Space Telescope. GLAST Large Area Telescope: Electronics, Data Acquisition & Flight Software TEM Power Supply Part 1 Gunther Haller Stanford Linear Accelerator Center Manager, Electronics, DAQ & FSW LAT Chief Electronics Engineer haller@slac.stanford.edu

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GLAST Large Area Telescope: Electronics, Data Acquisition & Flight Software TEM Power Supply

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  1. Gamma-ray Large Area Space Telescope GLAST Large Area Telescope: Electronics, Data Acquisition & Flight Software TEM Power Supply Part 1 Gunther Haller Stanford Linear Accelerator Center Manager, Electronics, DAQ & FSW LAT Chief Electronics Engineer haller@slac.stanford.edu (650) 926-4257

  2. LAT Electronics Physical TKR Front-End Electronics (MCM) 16 Tower Electronics Modules • DAQ electronics module (DAQ-EM) • Power-supplies for tower electronics ACD Front-End Electronics (FREE) TKR CAL Front-End Electronics (AFEE) CAL Global-Trigger/ACD-EM/Signal-Distribution (GAS) Unit* 3 Event-Processor Units (2+1 spare) • Event processing CPU • LAT Communication Board (LCB) • Storage Interface Board (SIB) Spacecraft Interface Unit • Storage Interface Board (SIB): EEPROM SC MIL1553 control & data • LAT control CPU • LAT Communication Board (LCB): LAT command and data interface Power-Distribution Unit (PDU)* • Spacecraft interface, power • LAT power distribution • LAT health monitoring * Primary & Secondary Units shown in one chassis

  3. LAT Power Distribution • SIU’s are powered directly by spacecraft on dedicated feeds • Rest of LAT electronics is powered via SC main feed to PDU • Prime and redundant SC feeds connected to prime and redundant PDU circuits • PDU controls power to towers, to GASU, and to EPU’s • Either PDU circuit can supply power to clients • GASU switches power to ACD • Prime and redundant GASU circuit can supply power to ACD • TEM’s switch power to TKR/CAL • No redundancy in tower power system • Heater power circuit not shown

  4. Requirements • Requirements are in LAT-SS-01281 • Supply power to Calorimeter, Tracker, TEM-DAQ systems • Main drivers are • Low output noise, down to 100 uV RMS, 1 mV p-p • Powers input amplifiers of CAL and TKR front-end electronics • Low output voltage, down to 1.5 V • TKR input amplifier runs of 1.5V to meet power/thermal requirements for 850k channels • High overall efficiency • Total LAT power limited, also thermal limits because of radiator area • Adjustable high-voltage supply up to 150V • Silicon strip TKR detectors (up to 150V) and CAL Si-diodes (up to 100V) need remotely adjustable depletion voltages

  5. Detailed Requirements • See LAT-SS-1281, (display the requirement pages in that document for discussion)

  6. Tower Power Supply Module TRK-Enable Ana-1.5V-A (~1A) Ana-1.5V-B (~1A) Tracker Voltages Ana-2.5V-A (~1A) Ana-2.5V-B (~1A) Dig-2.5V-A (~0.3A) Dig-2.5V-B (~0.3A) HV-150Vadj- (~1uA) 28V from PDU 461-Filter HV-I MON Ana-3.3V (~0.4A) Calorimeter Voltages Dig-3.3V (~0.96A) HV-100Vadj- (~1uA) CAL-Enable HV-I MON Dig-3.3V-del (~0.6A) TEM-DAQ Voltages Dig-2.5V (~0.4 A) Currents are measured values To PDU Temp, 3.3V TEM-V Sensors I-Total MON

  7. Tracker Electronics • TKR sub-system electronics • Si-Strip Detectors • 24 GTFE (GLAST Tracker Front-End) ASICs (1,536 signal channels) • 2 GTRC (GLAST Tracker Readout Controller) ASICs • MCM (Multi-Chip Module) • Flex-cables • Total of 36 (4 sides, 9 each) MCM’s per tower power supply module • Power is routed via TEM DAQ board from TEM-PS to TKR GTRC ASIC GTFE ASIC

  8. Calorimeter Electronics • CAL sub-system electronics • Diodes • 48 GCFE (GLAST Calorimeter Front-End) ASICs • 4 GCRC (GLAST Calorimeter Readout Controller) ASICs • AFEE (Analog Front-End Electronics) board • Total of 4 (4 sides, 1 each) AFEE’s per tower power supply module • Power is routed via TEM DAQ board from TEM-PS to CAL GCRC ASIC GCFE ASIC

  9. DAQ Electronics • Tower Electronics Module DAQ board • Total of 1 TEM DAQ per tower power supply module

  10. Interfaces • Tower Power Supply interface via two connectors to • Power Distribution Unit • Incoming 28V +/- 1V • Monitoring to PDU • For EGSE desire to be able to remotely adjust front-end voltages • Tower Electronics Module • Supply voltages to TKR, CAL, and TEM • HV currents and total current monitoring • Enable signals for CAL and TKR system • Analog set voltage for HV supplies • LAT-SS-1281

  11. Enclosure PSU Tower Electronics Module TEM – PSU Stack

  12. Development • When SLAC electronics group started getting involved in LAT electronics (at approval of project) • Efficiency of power supplies of tower was supposed to be about 70% overall to meet power numbers • Tried to get more power, but denied • SC interface issue • Problem with getting rid of heat (radiator areas) • Worked to even more optimizing CAL, TKR, DAQ power (ASIC’s and other components), • Reduced power supply efficiency required to 62% (still very challenging, but that was it) • Standard solution with “catalog” 28V/3.3V DC/DC converter and linear regulators were explored but not realistic • At tower load of ~25W, needed at least 40W (at 3.3V!) converter, (no 1.5V or 2.5V converter available at that time) • At LAT load: efficiency is 65% to 70%. just for 28->3.3V part • Need to generate 2.5V and 1.5V via linear regulators from 3.3V • Results in 47-50% overall efficiency (including HV supplies) • Over allocation: between 88W and 126W

  13. Development (Con’t) • First solution • Pursued full-custom vendor design • Proof-of-principle prototype was designed and built, based on synchronous rectification • Measured 87% efficiency of 28V/1.5V supply! • Met power requirement (status at CDR) • Went out for bids (Responses came in after CDR) • Bid returned were not affordable, by a lot • Not a working solution

  14. Development (Con’t) • Beginning of 04 • International Rectifier proposed new Z-series converter, based on synchronous rectification • 28V/3.3V converter with up to 82% efficiency at full load, great device compared to others on the market • New Device (no flight heritage yet), assembly of two PC-boards and controller hybrid

  15. Development (Con’t) • Needed to be optimized for LAT load (Z-series is optimized for 20A/3.3V (~82%), LAT only needs 40% of that -> efficiency drops considerably) • Put contract in place late spring 03 (as back-up) • However still does not meet power allocation by > 30W • Prototypes to be delivered late Fall 03 • On order, but cancelable (need to decide end of 9/03 with penalty of 10%) • Risk that calorimeter 3.3V analog is connected to DAQ TEM 3.3V, very hard to filter low frequency noise from DAQ • Need to decide by end of 9/03 to avoid further penalty

  16. Development (Con’t) • Spring 03: • Surveyed commercial DC/DC converters and evaluated for potential radiation performance (CMOS versus bipolar technology, IC feature sizes) • Radiation tested several DC/DC integrated circuit devices at Legnaro and TAMU (in Summer 03) • Selected MAX724/726 devices as base-line • Designed circuit board for low-voltage circuits using MAX726 • Designed high-voltage circuit (all along needed to be full-custom since nothing available as a catalog item) • Received also proof-of-principle HV design from vendor (at CDR) • Went out for bids • Was not affordable, by a lot • Got previous flight design from Art Ruitberg (GSFC) • Started new design at SLAC (Dieter Freytag), eliminating transformers

  17. Development (Con’t) • Designed/simulated high-voltage circuit by 7/03 • Laid out HV-only PC board, fabricate/loaded by 8/03 • Designed/laid-out/fabricated full TEM-PS by end of August 03 • Started testing 9/03 • Review 9/22/03

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