GLAST LAT Project October 23 2003 GLAST Large

GLAST LAT Project October 23, 2003 GLAST Large Area Telescope: Gamma-ray Large Area Space Telescope Tracker Subsystem WBS 4. 1. 4 GTRC Review November 14, 2003 Robert Johnson Santa Cruz Institute for Particle Physics University of California at Santa Cruz Tracker Subsystem Manager rjohnson@scipp. ucsc. edu GTRC Mini-Review Tracker, WBS 4. 1. 4 1

GLAST LAT Project October 23, 2003 GTRC Specifications The GTRC serves as the interface between a front-end electronics module (MCM) and other MCMs and the data acquisition (TEM). GTRC Mini-Review Tracker, WBS 4. 1. 4 2

GLAST LAT Project October 23, 2003 GTRC Specifications • The detailed specification is LAT-TD-00170. • An FPGA could not be used for reasons of space, power, and the need for differential I/O to avoid disturbing the amplifier chips. • Some notable features: – 20 MHz clock; 2. 5 V operation – All I/O is LVDS and serial – Configuration register that can be set and read back nondestructively – Zero-suppression of the GTFE data; memory for 64 hits – Buffering of all signals and clock to and from the GTFE chips, including the trigger signals, commands, data, etc. – Calculation and quadruple buffering of the TOT of the layer-OR trigger primitive – Double buffering of the data: allows collection of data from GTFE chips while sending the previous event to the TEM – Token-driven daisy-chain readout – Parity checking on all command data transfers – Trigger number checking to flag mixed events GTRC Mini-Review Tracker, WBS 4. 1. 4 3

GLAST LAT Project October 23, 2003 GTRC Description • All digital • Tanner standard-cells, except for • LVDS I/O cells. • SEU hardened configuration register. • RAM (64 hits, 2 buffers) • Design in VHDL; synthesis, auto place and route. • Agilent 0. 5 micron 3 -metal process GTRC Mini-Review Tracker, WBS 4. 1. 4 4

GLAST LAT Project October 23, 2003 GTRC History; 3 Generations • BTEM version (1999), designed by Gerrit Meddeler in the HP 0. 8 micron process. New LAT DAQ requirements and interface necessitated a major redesign. None of the old logic code or layout was retained. • GTRC V 1: functional, with flip-flop memory, but several bugs • GTRC V 2: nonfunctional due mainly to clock routing problems • GTRC V 3 and V 4: simultaneous submissions. V 3 had RAM and V 4 used flip flops (only 32 hits). The V 3 is the one reviewed last December at SLAC. – Lacking 4 buffering of the TOT (won’t align with events) – Failed to report some parity errors – Slow LVDS receivers • GTRC V 5: interim prototype submission, parasitic on another run, before complete testing of the V 3 was done, to fix the TOT and parity • GTRC V 6: “flight submission” dedicated run; included the fixes in V 5 plus speeding up of the drivers and receivers. GTRC Mini-Review Tracker, WBS 4. 1. 4 5

GLAST LAT Project October 23, 2003 Tracker Electronics Test Systems • Wafer Testing (GTFE and GTRC) – Procedure documented in LAT-PS-1250 – Test vectors documented in LAT-TD-247 and LAT-TD-248 – Verifies LVDS levels and power consumption as well as function – The GTRC vectors (LAT-TD-248) have been augmented with a test used to verify the GTRC V 6 TOT bug • MCM Testing – Procedure documented in LAT-PS-1971 – Test vectors documented in LAT-TD-249 – Verifies LVDS levels, power consumption and leakage, all functionality, and limited performance testing (no SSDs) – Tests different frequencies and different VDD levels • Burn-in System (documentation in progress, LAT-TD-2367) – Tests a complete tower of MCMs together with TEM – Includes thermal cycling for environmental acceptance tests – Repeatedly executes a set of test vectors while at elevated temperature GTRC Mini-Review Tracker, WBS 4. 1. 4 6

GLAST LAT Project October 23, 2003 GTRC V 6 Design Problems • GTRC Time Over Threshold: – Logic in existing chip is flawed (causes frequent DAQ time-outs) and can only be repaired by repeating the production. The existing V 6 chip can only be used with the time-over-threshold disabled. – The problem occurs when a second trigger is received in coincidence with the falling edge of the time-over-threshold. – This was verified both in VHDL and on bare die driven by the wafer probing system. – The fault was not caught until a complete system was put together and run on cosmic rays. It would be unlikely to be noticed without a random event source and lots of events. – The TOT algorithm can be done in the TEM ASIC (GTCC). This was tested in the FPGAs of an EM TEM. There are even some data throughput advantages to doing it in the TEM. GTRC Mini-Review Tracker, WBS 4. 1. 4 7

GLAST LAT Project October 23, 2003 GTRC V 6 Design Problems • GTRC to GTRC data transfer and timing margins: – The data are output from one GTRC on the falling edge of the clock (a clear mistake in retrospect) and were supposed to be captured in the next GTRC on the rising edge of the next clock 25 ns later. Simulations during the design phase indicated no problem with this, but they did not include enough of the parasitic capacitance. – At 20 MHz the system was running well, but only by consistently missing the data on the first clock edge and capturing it 50 ns later. The problem was seen when the frequency was lowered. – Our test plan was deficient in not looking much more closely at this data transfer early on. Even with the V 3 we looked at some different frequencies but did not stumble upon the problem. – The observed internal delays are now understood in simulation. – The design is easy to fix. Big margins at 20 MHz can be achieved by simply removing the clock inversion, but schedule… GTRC Mini-Review Tracker, WBS 4. 1. 4 8

GLAST LAT Project October 23, 2003 GTRC Data Transmission To GTFEs A CLK C GTRC-1 GTRC-0 B D Q D Q This inverter drives several flip flops in widely separated core locations, resulting in a significant delay of data output. • Measured ~28 ns delay from A to B is well understood now in terms of agreement between simulation and measurements. • The ~19 ns delay from A to C also agrees well with simulations. GTRC Mini-Review Tracker, WBS 4. 1. 4 9

GLAST LAT Project October 23, 2003 Impact of GTRC Timing Problem • Using the existing chips: – At 20 MHz and 2. 5 V they skip a clock on each transfer. • Not a problem in itself (same timing as would be achieved by output on the rising edge), BUT – Fails if the frequency is lowered to 19 MHz. – Fails at 20 MHz if the voltage is raised. – It works properly up to about 15 MHz at 2. 44 V, or to higher frequency if the voltage is raised (but insufficient power to fix the problem). – The frequency limit of correct operation can be raised a little by lowering the termination resistance, with 200 -ohm external resistors placed in parallel with the existing internal 700 ohms. • Requires 16 resistors on each flex-circuit cable (not difficult or expensive). • Still cannot achieve 20 MHz with good margins. GTRC Mini-Review Tracker, WBS 4. 1. 4 10

GLAST LAT Project October 23, 2003 Timing Margins for GTRC V 6 2. 29 V 2. 56 V Improperation Properation • Measurements made on a string of 9 MCMs (i. e. one tower side) connected to a TEM via burn-in flex-circuit cables, using connectors savers. • No additional termination resistors have been added to the system. • The voltages listed here are measured at the chips. The voltage at the TEM is higher. GTRC Mini-Review Tracker, WBS 4. 1. 4 11

GLAST LAT Project October 23, 2003 Timing Margins for GTRC V 6 2. 84 V The Agilent process is designed for maximum 3. 3 V operation. This slide shows the margins with the maximum voltage we can achieve with our existing TEM/PS. Probably the margin will continue to increase if we push up to 3. 3 V. GTRC Mini-Review Tracker, WBS 4. 1. 4 12

GLAST LAT Project October 23, 2003 GTRC V 6 with 200 -ohm Termination • Adding 200 ohms in parallel with the existing 700 ohm termination speeds up the rise time of the signal on the cable between GTRC chips and raises a little the maximum operational frequency. • We did not finish the complete survey of this condition because the TEM broke during the measurements and the unencapsulated test MCMs were losing their wire bonds. • Safe operation could be achieved at about 16 MHz with the voltage at the TEM raised from 2. 5 V to 2. 75 V. Maximum frequency of properation. Temperature 2. 45 V at TEM 25°C Voltage at TEM Maximum freq. 15. 8 MHz 2. 46 15. 5 MHz 30°C 15. 8 MHz 2. 61 17. 0 MHz 35°C 15. 6 MHz 2. 76 18. 5 MHz 40°C 15. 4 MHz 2. 93 19. 6 MHz 45°C 15. 3 MHz 3. 00 20. 2 MHz 50°C 15. 1 MHz 3. 08 20. 6 MHz GTRC Mini-Review 2. 61 V at TEM Measurements at 25 °C 17. 2 MHz 16. 0 MHz Tracker, WBS 4. 1. 4 13

GLAST LAT Project October 23, 2003 Tracker Power • Measurements made this week at 20 MHz with the latest MCMs. • Assuming 4 A/SSD at 120 V bias (total of 4. 4 W of bias power). • CDR allocation: 155 W. GTRC Mini-Review Tracker, WBS 4. 1. 4 14

GLAST LAT Project October 23, 2003 Mini-Tower Hit Efficiency From Hiro Tajima, measured using cosmic rays under 3 different trigger conditions. 5 layers are used for tracking (exactly 5 clusters required, with straight track in the view with 3 hits); the 6 th layer is used to find the hit efficiency, including cutting away from dead areas between wafers. The peak amplifier pulse height occurs at about 1. 0 to 1. 5 s TACK delay. For the EXT trigger (scintillator), zero on this scale is about 0. 9 s after passage of the particle. GTRC Mini-Review Tracker, WBS 4. 1. 4 15

GLAST LAT Project October 23, 2003 Impact of Loss of TOT • While not originally thought to be necessary in order to meet our science requirements, the TOT has recently been found to be important in greatly reducing a troublesome background source: – Cosmic ray hits the calorimeter from below or from the side. – A proton or heavy ion exits the calorimeter, enters the Tracker, and stops several layers up in the Tracker. – This topology can look very much like a photon conversion, but the stopping ion produces a very large ionization that can be readily distinguished from relativistic electrons. GTRC Mini-Review Tracker, WBS 4. 1. 4 16

GLAST LAT Project October 23, 2003 TOT Analysis (Simulation) TOT Asymmetry between 1 st 3 and last 3 planes. 100 Me. V Gammas Albedo Protons TOT Average GTRC Mini-Review Tracker, WBS 4. 1. 4 TOT here is truncated to 250 counts by GTRC 17

GLAST LAT Project October 23, 2003 TOT Analysis (Simulation) The asymmetry is not useful with the 50 microsecond truncation imposed in the GTRC design. But the average TOT still gives good separation, only about 10% worse than with no truncation. GTRC Mini-Review Tracker, WBS 4. 1. 4 18

GLAST LAT Project October 23, 2003 Background Analysis (Simulation) Remaining Background Analysis of 25 M MC Mixed BKG Events (Bill Atwood) Generated cos 3 Classes of Background Events Remain: • Range-outs from below (. 04 Hz) • Horizontal Events (. 004 Hz) • ACD Leakage and inefficiency (. 04 Hz) Elimination Strategy Measured cos Aeff & Background Rate: Aeff = 8400 cm 2 on Axis (E > 3 Ge. V) Aeff x DW = 2. 0 m 2 -str BUT. . Background Rate 4 -5 times too high GTRC Mini-Review 1) Range-outs - To. T Identification in Tracker - kills > 90% - MIP Identification in CAL - should kill > 50% 2) Horizontal Events - should kill > 50% - Edge CAL hits 3) ACD Leakage - Events found accurately; - Cover cracks with Tapes - should kill > 95% Estimated Rate after this to be <. 006 Hz (about 3% residual background in EGD signal) Tracker, WBS 4. 1. 4 19

GLAST LAT Project October 23, 2003 New GTRC Designs • GTRC V 7: the new flight design – TOT algorithm rewritten to fix the bug – Clock inversion removed for the data output, token output, and trigger-request output – Recompiled logic core; no changes outside the logic core • GTRC V 6 b: backup design in case V 7 fails – Clock inversion removed by hand edit of the layout and schematic; verified by LVS – Essentially identical to the V 6 chips modified by FIB (see below) GTRC Mini-Review Tracker, WBS 4. 1. 4 20

GLAST LAT Project October 23, 2003 GTFE V 7 Design Verification • VHDL simulation of the logic core. Note that there are no changes between V 6 and V 7 outside of the logic core. • Recompiled logic core is grafted into the old V 6 layout, replacing only the old logic core. • Usual LVS and DRC of the new layout. • Nanosim simulation of the complete extracted netlist. • Verification of the logic core in FPGAs • FIB removal of the culprit inverter in 6 GTRC V 6 chips and tests on MCMs GTRC Mini-Review Tracker, WBS 4. 1. 4 21

GLAST LAT Project October 23, 2003 Test of FIB Patched GTRC • Layout was modified by ion beam to send data and token out on the rising clock edge. GTRC-1 Data Out • These scope traces show transmission of register readback data. 1 MHz GTRC-0 Data Out Data output from GTRC 1 on this edge. Data output from GTRC 0 on this edge. Clock In Data captured by GTRC 0 on this edge. GTRC Mini-Review Tracker, WBS 4. 1. 4 22

GLAST LAT Project October 23, 2003 Test of FIB Patched GTRC Note the long time constant from the cable capacitance times the 700 ohm impedance. 20 MHz GTRC-1 Data Out GTRC-0 Data Out Data output from GTRC 1 on this edge. GTRC Mini-Review Data output from GTRC 0 on this edge. Clock In Tracker, WBS 4. 1. 4 23

GLAST LAT Project October 23, 2003 Test of FIB Patched GTRC • Three of the patched GTRC chips were operated on separate MCMs and read out in a chain using burn-in cables with connector savers. • All frequencies above 5 MHz were tested (in 0. 1 MHz steps). • Both register readback and data (charge injection) are tested. • The results below are at room temperature, but the test was also carried out from – 20°C to +60°C with very similar results. • The upper frequency limit is consistent with the internal limitations of the MCMs. Voltage on MCM at Chips Maximum Frequency of Proper Operation. 2. 29 V 25 MHz 2. 56 V 27 MHz 2. 84 V 29 MHz GTRC Mini-Review Tracker, WBS 4. 1. 4 24

GLAST LAT Project October 23, 2003 Test of FIB Patched GTRC • The string of 9 MCMs, including those with FIB patched GTRC chips, was taken to SLAC and operated with the new TEM that has ASIC cable controller chips (GTCC). • This system also operated at all frequencies from 1 MHz to about 29 MHz. • Again, the limit is the communication within the MCM, not the GTRC/GTCC communication. • We also repeated frequency margin tests at UCSC on individual MCMs to verify that they operate at all frequencies from 1 MHz to close to about 29 MHz. GTRC Mini-Review Tracker, WBS 4. 1. 4 25

GLAST LAT Project October 23, 2003 Test of V 7 VHDL Code • We have installed the updated VHDL code into 3 FPGA test boards. Each test board has 2 FPGAs, which play the GTRC role, and 2 GTFE amplifier chips. • Two FPGA test boards are being operated with the TEM system and the GTFE chips, and no problems have been so far with reading back registers and charge-injection “data”. • The third FPGA test board was modified to be operated directly from a COM card (VME I/O card), with the GTFE chips disconnected. This allows us to input fake “GTFE data” into the GTRC FPGA directly from the VME. In this way we can execute the complete set of GTRC wafer test vectors (see LAT-TD-00248) through the new VHDL code. – No problems seen in execution of the test vectors. – The TOT problem seen in V 6 chips does not show up in this test. GTRC Mini-Review Tracker, WBS 4. 1. 4 26

GLAST LAT Project October 23, 2003 GTRC V 7 Test Plan • Wafer testing at UCSC (start immediately upon receipt of wafers) – Complete system exists and is flight-production qualified (and will still be within the 1 -year calibration time frame). – We will get it running smoothly again before arrival of the new wafers, using an old wafer and the old wafer map. – However, a new wafer map must be carefully prepared in advance. – All of the test vectors (LAT-TD-00248 plus the new TOT test) have already been run through the V 7 logic code in the FPGA, so this test is very unlikely to turn up any logic bugs. – Test and ink enough wafers for all of GLAST in a day or two. – We will test both V 7 and V 6 b dice, just in case. • Wafer dicing and inspection at GDSI – Get PO in place and grease the skids in advance. – No change with respect to the previous procedure used on V 6, except that the reticle layout is new. – It should be possible to complete this within a week. GTRC Mini-Review Tracker, WBS 4. 1. 4 27

GLAST LAT Project October 23, 2003 GTRC V 7 Test Plan • Dice 1 wafer immediately (by MOSIS? ). • Borrow Mike Huffer’s MCMs, which are not encapsulated. • Put V 7 chips on 1 MCM and test it. – One of two test system, identical to the test system presently at Teledyne for MCM production testing. – Test vectors are documented in LAT-TD-00249. – This should take less than a day. • Put V 7 chips on 8 more MCMs and install a full readout string of 9 MCMs into the burn-in system. – Uses the standard TEM-based EGSE system. – All of the hardware exists now, but work is still in progress to complete the set of test vectors. – Test over the full frequency, voltage, and temperature ranges. • The burn-in system is already set up for thermal cycling. GTRC Mini-Review Tracker, WBS 4. 1. 4 28

GLAST LAT Project October 23, 2003 GTRC V 7 Test Plan • Replace the GTRCs on the rest of Huffer’s 36 MCMs with V 7 chips. – Test each one with the MCM test system. – Install 36 back into the test setup of the electronics group for further testing. • Meanwhile, MCM production at Teledyne is proceeding with V 7 chips, just as soon as the wafers are diced. – Rush the first lot of completed, tested, burned-in flight MCMs to Italy for integration onto trays. – The first n trays assembled go into the stacked-tray test system, where they are coupled to the EGSE by flex-circuit cables. • Here the new chips see cosmic-ray data for the first time. • This test system can execute practically the complete set of tower test scripts before tower assembly takes place and even without a complete tower of trays. GTRC Mini-Review Tracker, WBS 4. 1. 4 29

GLAST LAT Project October 23, 2003 GTRC V 7 Test Plan • Radiation Testing – Repeat TID testing using the new V 7 chips. – Repeating the heavy-ion testing should not be necessary, but if required, we could do it again in Italy (for SEU testing). • Qualification Testing – We will move forward with qualification testing using MCMs from the preproduction run presently in progress (GTRC V 6 chips). • Thermal cycling • Extended burn-in • Vibration testing • DPA – This will have to be repeated with MCMs from the flight lots. GTRC Mini-Review Tracker, WBS 4. 1. 4 30