GLAST LAT ProjectOctober 23, 2003 GTRC Mini-Review Tracker, WBS GLAST Large Area Telescope: Tracker Subsystem WBS GTRC Review November 14, 2003 Robert Johnson Santa Cruz Institute for Particle Physics University of California at Santa Cruz Tracker Subsystem Manager Gamma-ray Large Area Space Telescope

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

GLAST LAT ProjectOctober 23, 2003 GTRC Mini-Review Tracker, WBS GTRC Specifications The detailed specification is LAT-TD 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 and data transfers –Trigger number checking to flag mixed events

GLAST LAT ProjectOctober 23, 2003 GTRC Mini-Review Tracker, WBS 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

GLAST LAT ProjectOctober 23, 2003 GTRC Mini-Review Tracker, WBS 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 V1: functional, with flip-flop memory, but several bugs GTRC V2: nonfunctional due mainly to clock routing problems GTRC V3 and V4: simultaneous submissions. V3 had RAM and V4 used flip flops (only 32 hits). The V3 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 V5: interim prototype submission, parasitic on another run, before complete testing of the V3 was done, to fix the TOT and parity GTRC V6: “flight submission” dedicated run; included the fixes in V5 plus speeding up of the drivers and receivers.

GLAST LAT ProjectOctober 23, 2003 GTRC Mini-Review Tracker, WBS 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 V6 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

GLAST LAT ProjectOctober 23, 2003 GTRC Mini-Review Tracker, WBS GTRC V6 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 V6 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.

GLAST LAT ProjectOctober 23, 2003 GTRC Mini-Review Tracker, WBS GTRC V6 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 25ns 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 50ns 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 V3 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…

GLAST LAT ProjectOctober 23, 2003 GTRC Mini-Review Tracker, WBS GTRC Data Transmission 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. DQDQDQDQ A B CLK GTRC-1GTRC-0 To GTFEs C This inverter drives several flip flops in widely separated core locations, resulting in a significant delay of data output.

GLAST LAT ProjectOctober 23, 2003 GTRC Mini-Review Tracker, WBS Impact of GTRC Timing Problem Using the existing chips: –At 20 MHz and 2.5V 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 2.44V, 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.

GLAST LAT ProjectOctober 23, 2003 GTRC Mini-Review Tracker, WBS Timing Margins for GTRC V6 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 V 2.56 V Proper operation Improper operation

GLAST LAT ProjectOctober 23, 2003 GTRC Mini-Review Tracker, WBS Timing Margins for GTRC V V The Agilent process is designed for maximum 3.3V 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 3.3V.

GLAST LAT ProjectOctober 23, 2003 GTRC Mini-Review Tracker, WBS GTRC V6 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 proper operation. Temperature2.45 V at TEM2.61 V at TEM 25°C15.8 MHz 30°C15.8 MHz 35°C15.6 MHz17.2 MHz 40°C15.4 MHz 45°C15.3 MHz16.0 MHz 50°C15.1 MHz Measurements at 25 °C Voltage at TEMMaximum freq MHz MHz MHz MHz MHz MHz

GLAST LAT ProjectOctober 23, 2003 GTRC Mini-Review Tracker, WBS 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.

GLAST LAT ProjectOctober 23, 2003 GTRC Mini-Review Tracker, WBS 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. For the EXT trigger (scintillator), zero on this scale is about 0.9  s after passage of the particle. The peak amplifier pulse height occurs at about 1.0 to 1.5  s TACK delay.

GLAST LAT ProjectOctober 23, 2003 GTRC Mini-Review Tracker, WBS 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.

GLAST LAT ProjectOctober 23, 2003 GTRC Mini-Review Tracker, WBS TOT Analysis (Simulation) 100 MeV GammasAlbedo Protons TOT Asymmetry between 1 st 3 and last 3 planes. TOT Average TOT here is truncated to 250 counts by GTRC

GLAST LAT ProjectOctober 23, 2003 GTRC Mini-Review Tracker, WBS 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.

GLAST LAT ProjectOctober 23, 2003 GTRC Mini-Review Tracker, WBS Background Analysis (Simulation) 3 Classes of Background Events Remain: Range-outs from below (.04 Hz) Horizontal Events (.004 Hz) ACD Leakage and inefficiency (.04 Hz) Elimination Strategy 1) Range-outs - ToT 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) A eff & Background Rate: A eff = 8400 cm 2 on Axis (E > 3 GeV) A eff x  = 2.0 m 2 -str BUT.... Background Rate 4-5 times too high Remaining Background Measured cos  Generated cos  Analysis of 25M MC Mixed BKG Events (Bill Atwood)

GLAST LAT ProjectOctober 23, 2003 GTRC Mini-Review Tracker, WBS New GTRC Designs GTRC V7: 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 V6b: backup design in case V7 fails –Clock inversion removed by hand edit of the layout and schematic; verified by LVS –Essentially identical to the V6 chips modified by FIB (see below)

GLAST LAT ProjectOctober 23, 2003 GTRC Mini-Review Tracker, WBS GTFE V7 Design Verification VHDL simulation of the logic core. Note that there are no changes between V6 and V7 outside of the logic core. Recompiled logic core is grafted into the old V6 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 V6 chips and tests on MCMs

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

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

GLAST LAT ProjectOctober 23, 2003 GTRC Mini-Review Tracker, WBS 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 ChipsMaximum Frequency of Proper Operation V25 MHz 2.56 V27 MHz 2.84 V29 MHz

GLAST LAT ProjectOctober 23, 2003 GTRC Mini-Review Tracker, WBS 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.

GLAST LAT ProjectOctober 23, 2003 GTRC Mini-Review Tracker, WBS Test of V7 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 seen 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 V6 chips does not show up in this test.

GLAST LAT ProjectOctober 23, 2003 GTRC Mini-Review Tracker, WBS GTRC V7 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 plus the new TOT test) have already been run through the V7 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 V7 and V6b 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 V6, except that the reticle layout is new. –It should be possible to complete this within a week.

GLAST LAT ProjectOctober 23, 2003 GTRC Mini-Review Tracker, WBS GTRC V7 Test Plan Dice 1 wafer immediately (by MOSIS?). Borrow Mike Huffer’s MCMs, which are not encapsulated. Put V7 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 –This should take less than a day. Put V7 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.

GLAST LAT ProjectOctober 23, 2003 GTRC Mini-Review Tracker, WBS GTRC V7 Test Plan Replace the GTRCs on the rest of Huffer’s 36 MCMs with V7 chips. –Test each one with the MCM test system. –Install all 36 back into the test setup of the electronics group for further testing. Meanwhile, MCM production at Teledyne is proceeding with V7 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.

GLAST LAT ProjectOctober 23, 2003 GTRC Mini-Review Tracker, WBS GTRC V7 Test Plan Radiation Testing –Repeat TID testing using the new V7 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 V6 chips). Thermal cycling Extended burn-in Vibration testing DPA –This will have to be repeated with MCMs from the flight lots.