GLAST LAT ProjectTower Power Supply Review Sept 22, 2003 Gunther HallerPart 1, Version 3 1 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 (650) Gamma-ray Large Area Space Telescope

GLAST LAT ProjectTower Power Supply Review Sept 22, 2003 Gunther HallerPart 1, Version 3 2 LAT Electronics Physical 16 Tower Electronics Modules –DAQ electronics module (DAQ-EM) –Power-supplies for tower electronics * Primary & Secondary Units shown in one chassis 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 Global-Trigger/ACD-EM/Signal-Distribution (GAS) Unit* TKR CAL TKR Front-End Electronics (MCM) ACD Front-End Electronics (FREE) CAL Front-End Electronics (AFEE)

GLAST LAT ProjectTower Power Supply Review Sept 22, 2003 Gunther HallerPart 1, Version 3 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

GLAST LAT ProjectTower Power Supply Review Sept 22, 2003 Gunther HallerPart 1, Version 3 4 Requirements Requirements are in LAT-SS 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

GLAST LAT ProjectTower Power Supply Review Sept 22, 2003 Gunther HallerPart 1, Version 3 5 Detailed Requirements See LAT-SS-1281, (display the requirement pages in that document for discussion)

GLAST LAT ProjectTower Power Supply Review Sept 22, 2003 Gunther HallerPart 1, Version 3 6 Tower Power Supply Module Tracker Voltages Ana-1.5V-A (~1A) Ana-1.5V-B (~1A) 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) Calorimeter Voltages Ana-3.3V (~0.4A) Dig-3.3V (~0.96A) HV-100Vadj- (~1uA) TEM-DAQ Voltages Dig-3.3V-del (~0.6A) Dig-2.5V (~0.4 A) Temp, 3.3V TEM- V Sensors 461-Filter 28V from PDU To PDU TRK- Enable CAL- Enable HV-I MON I-Total MON Currents are measured values

GLAST LAT ProjectTower Power Supply Review Sept 22, 2003 Gunther HallerPart 1, Version 3 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 GTFE ASIC GTRC ASIC

GLAST LAT ProjectTower Power Supply Review Sept 22, 2003 Gunther HallerPart 1, Version 3 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 GCFE ASIC GCRC ASIC

GLAST LAT ProjectTower Power Supply Review Sept 22, 2003 Gunther HallerPart 1, Version 3 9 DAQ Electronics Tower Electronics Module DAQ board Total of 1 TEM DAQ per tower power supply module

GLAST LAT ProjectTower Power Supply Review Sept 22, 2003 Gunther HallerPart 1, Version 3 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

GLAST LAT ProjectTower Power Supply Review Sept 22, 2003 Gunther HallerPart 1, Version 3 11 Enclosure TEM – PSU Stack Tower Electronics Module PSU

GLAST LAT ProjectTower Power Supply Review Sept 22, 2003 Gunther HallerPart 1, Version 3 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

GLAST LAT ProjectTower Power Supply Review Sept 22, 2003 Gunther HallerPart 1, Version 3 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

GLAST LAT ProjectTower Power Supply Review Sept 22, 2003 Gunther HallerPart 1, Version 3 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

GLAST LAT ProjectTower Power Supply Review Sept 22, 2003 Gunther HallerPart 1, Version 3 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

GLAST LAT ProjectTower Power Supply Review Sept 22, 2003 Gunther HallerPart 1, Version 3 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

GLAST LAT ProjectTower Power Supply Review Sept 22, 2003 Gunther HallerPart 1, Version 3 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