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

GLAST LAT Project Tower Power Supply Review Sept 22, 2003

Gunther Haller Part 1, Version 3 1

GLAST Large Area Telescope:GLAST Large Area Telescope:

Electronics, Data Acquisition & Flight Software TEM Power SupplyPart 1

Gunther HallerStanford Linear Accelerator CenterManager, Electronics, DAQ & FSWLAT Chief Electronics Engineer

[email protected](650) 926-4257

Gamma-ray Large Gamma-ray Large Area Space Area Space TelescopeTelescope



LAT Electronics PhysicalLAT Electronics Physical

16 Tower Electronics Modules– DAQ electronics module (DAQ-EM)– Power-supplies for tower electronics

* Primary & Secondary Units shown in one chassis

ACD

spare

EPU-3

EPU-2EPU-1

spare spare

Pwr Dist. Box

GASU

spare

spare

SIU-P SIU-R

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)



LAT Power DistributionLAT Power Distribution

ACD

ACD

ACD

PDUBoard P

EPUP0

SC MainFeed P

0 1 11

EPUP1

EPUR

SIUR

SIUP

TEMDAQ

CAL

TKR

Power Distribution

PDUBoard R

TEMDAQ

CAL

TKR

TEMDAQ

CAL

TKR

TEMDAQ

CAL

TKR

SC SIU RFeed

PDUPrimeRedundant

SC SIU PFeed

SC MainFeed R

GASUDAQ P

GASUDAQ R

ACD PSP

ACD PSR

GASUTowerPS

TEM0

TowerPS

TowerPS

TowerPS

TEM1

TEM14

TEM15

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



RequirementsRequirements

• 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



Detailed RequirementsDetailed Requirements

• See LAT-SS-1281,

(display the requirement pages in that document for discussion)



Tower Power Supply ModuleTower 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-Filter28V from PDU

To PDU

TRK-Enable

CAL-Enable

HV-I MON

HV-I MON

I-Total MON

Currents are measured values



Tracker ElectronicsTracker 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



Calorimeter ElectronicsCalorimeter 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



DAQ ElectronicsDAQ Electronics

• Tower Electronics Module DAQ board

• Total of 1 TEM DAQ per tower power supply module



InterfacesInterfaces

• 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



EnclosureEnclosure

TEM – PSU StackTower Electronics Module

PSU



DevelopmentDevelopment

• 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



Development (Con’t)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




• 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




– 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




• 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




• 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

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

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