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CPC2-CPR2 Testing

This article provides an overview of the testing and review process for CPC2-CPR2 assemblies, with a focus on the best results achieved using MB4.4. Topics covered include sparse readout, channel matching, and charge channels.

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CPC2-CPR2 Testing

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  1. CPC2-CPR2 Testing • Review • Best results from MB4.4 • Sparse readout • Testing with MB5 • Summary of CPR2 • Channel matching • Charge channels Tim Woolliscroft

  2. Overview of testing • Bump-bonded assemblies delivered from VTT • All single level metal CPC2 with single CPR2 • 12 CPC2-10, (10 passed DC probing at e2v), maybe additional loss to bond pad corrosion (analysis inconclusive) • 4 CPC2-40, (3 passed DC probing at e2v) • 2 CPC-70, (0 passed DC probing at e2v) • Breakdown by Motherboard • 1* MB4.2 ► 3 * CPC2-10 mounted, all failed (or failed soon after testing) • 2* MB4.4 ► 3 * CPC2-10 mounted, one fail ► MB4.4 #1 working well, best performance so far ► MB4.4 #2 high gain, voltage-charge section bias coupling • 2* MB5.0 ► MB5.0 #1 CPC2-40 mounted, with CPD1, working but high noise ► MB5.0 #1CPC2-40 remounted, new CPD1, untested ► MB5.0 #2 MB tested but not wire-bonded Tim Woolliscroft

  3. MB4.4 #1 Voltage channels • Best performance at 2MHz, 300mV ADC range • Optimise timing and biasing to reduce undershoot/overshoot • Simple analysis : • baseline restoration • signal inversion • Working well ADC 197 ADC 240 Tim Woolliscroft

  4. Higher Frequencies 5MHz (edge of chip) Gain seems to be dropping with frequency Suspect timing of ADCs and amplifiers 4MHz (edge of chip) Tim Woolliscroft

  5. MB4.4 #2Voltage channels • Shows Fe55 fits • But has remarkable gain • Data shown from 2.5V ADC range • Only 1.9 on board? • Many interesting features • Biasing of charge amps affects voltage channels • Current is slightly higher and dependant on Chip GND level • Showing some ADC sparkle codes • Works nothing like the other working assembly, previous settings and defaults would not work Tim Woolliscroft

  6. Noise Peak Fe55 Peak Second MB4.4 Only consistent feature! 300mV range MB4.4 #1 MB4.4 #2 1.5V range Tim Woolliscroft

  7. Cluster finder examples Its possible to test cluster finder! Although some channels always flag data for readout, multiplexer only visits them once each cycle. Its possible to “sneak” data through from good channels, if careful with occupancy. Junk data is hidden (due to garbled timestamp) Tim Woolliscroft

  8. Phase 1 Phase 2 CPC2-CPR2-CPD1 • First attempt at CPC2-CPR2-CPD1 • CPC2-40 SLM stitched CPC • Faults with CPDs of unknown origin, high current • Coupling between VDD and CPD_AV power supplies for CPD • Removed bond wires to CPD #1 • Halved the problem, power supplies stopped complaining so much, but still very high current (~1A continuous) • Can get clocks out of remaining CPD (max about 800mVpp & 1MHz) • Patched MB to provide second phase via the phase monitoring on bus bars • Despite problems have gained some results Tim Woolliscroft

  9. CPC2-CPR2-CPD1 1.5VPP Clocks CPR2 Voltage Amplifier output CPC Source follower output • No effects seen from stitching • Hit density uniform over all 2620 pixels • Reasonable performance from CPR2 voltage channels, normal levels of gain • but… CPC Source follower outputs Digitised by VME ADC Tim Woolliscroft

  10. CPR/CPC Channel Matching 300mV range MB4.4 #1 MB4.4 #2 MB5.0 Large channel to channel variation 1.5V range 400mV range Tim Woolliscroft

  11. 150mV Range CPR2 Charge Channels • Charge channels have not worked so far • Sensitive to biasing of CPR2 and CCD output, get either saturation or oscillation • Narrowing down the cause • Rule out interference from sparse logic → turn clocks off • Rule out timing → use settings that suit voltage amplifiers • Rule out interference from voltage ADCs → set constant code conversion • Rule out real time ADC output monitoring → look at analogue amplifier output • Tried all combinations of CCD output and charge amplifier biasing • CCD Charge injection, final test for charge amplifiers? • Used to provide larger signal to CPR2 charge amplifiers, up to 10k e- • Nothing seen on direct charge amplifier analogue output • Signal in charge channel ADCs consistent with interference from voltage section Injected signal Tim Woolliscroft

  12. CPR2 Charge Channels CPR1 charge channels worked, so what's changed? • Changes from CPR1 to CPR2 • ADC clock buffering on every channel • Change in feedback capacitor for increase gain (only on half of charge channels) • Back end of ADCs drives Direct ADC output, scan register, and sparse logic • Any thoughts Steve or Peter? • Many changes to Motherboards • Some undocumented or forgotten patch? • Changes to CPC outputs • Removal of wire bond pads • Wish we had CPR1 and CPR2 bump bonded to CPC2 • Try again at VTT? Konstantin’s CPR1 charge channel result Tim Woolliscroft

  13. Conclusion • CPC2-CPR2 testing is nearly complete • Last few assemblies on MB5.0 will be tested over the next month • Might be able to go a faster still • Some good results have been obtained • Voltage amplifiers and ADC have good performance at low clock speeds • Cluster finding logic demonstrated • But still have some unexplained • Reason for early failures • Charge amplifiers • Found some areas we need to improve • Many digital bugs will be fixed in CPR2a • Drop in gain towards middle of chip • Better analogue/ADC performance will have to wait till CPR3 Tim Woolliscroft

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