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Phase-1 test progress report (4)

Phase-1 test progress report (4). Discriminator transfer functions external reference voltages external bias traces removed optimization steps proposed by IPHC (after the IPHC-LBL meeting). External reference voltages (mean offset). Internal reference voltage External reference voltage.

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Phase-1 test progress report (4)

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  1. Phase-1 test progress report(4) Discriminator transfer functions external reference voltages external bias traces removed optimization steps proposed by IPHC (after the IPHC-LBL meeting)

  2. External reference voltages (mean offset) Internal reference voltage External reference voltage Figure of merit – RMS of the distribution (dispersion between columns) External reference voltage doesn’t reduce measured offset

  3. External reference voltages (std noise) Internal reference voltage External reference voltage Figure of merit – MEAN of the distribution (mean noise value for the sensor) External reference voltage doesn’t reduce measured noise

  4. External bias traces removed Cut traces Original configuration Removing traces doesn’t affect the measured dispersion and noise

  5. Optimization steps proposed by IPHC • e-mail dated 6/24 (2009) • Decrease VREF2 by 200 mV from the nominal value. VREF2 corresponds to the pixels output common mode voltage Step • Decrease ICLPDISC by 20%. This is the discriminator clamping voltage. • Example of IPHC measurements (Mimosa 26): • Before operation: Temporal Noise: 900 µV, FPN: 1000 µV • With step #1: Temporal Noise: 900 µV, FPN: 480 µv • With step #1+2: Temporal Noise: 880 µV, FPN: 370 µV

  6. Optimization steps • LBNL assessment: Default settings don’t work for Phase1 • VREF2 = 118 (nominal) doesn’t allow to perform a complete transfer function measurement for all channels (impossible to turn all pixels ON or OFF using only the available range of VREF1) REMINDER: threshold voltage is VTH= VREF2-VREF1 VREF2 range 0-2.5 V (step 10 mV) VREF1 range VREF2-32 mV to VREF2+32 mV (step 0.25 mV) • Testing procedure: • Select VREF2 (when VREF1=VREF2) so that pixels are at 50/50 below and above threshold. • Take a reference run with ICLPDISC= 100 (default) and a new run with ICLPDISC lowered by 20 % • Scan transfer functions for different VREF2 values, without changing IPIX. (Different from the previous sensor characterization performed before the IPHC-LBL meeting)

  7. Low discriminator clamping voltage Chip E3 (parameter scan) ICLPDISC=55 1.618 V ICLPDISC=80 1.841 V ICLPDISC=100 2.019 V (nominal) Mean noise value Threshold dispersion Confirms previous measurements : lower ICLIPDISC = less dispersion

  8. Low discriminator clamping voltage Chip D1 (parameter scan) ICLPDISC=55 1.648 V ICLPDISC=80 1.877 V ICLPDISC=100 2.060 V (nominal) Mean noise value Threshold dispersion Confirms previous measurements : lower ICLIPDISC = less dispersion

  9. Vref2 parameter scan (@ ICLPDISC = 80) Chip E3 (parameter scan) VREF2 = 81 0.852 V VREF2 = 82 0.863 V VREF2 = 83 0.873 V VREF2 = 84 0.885 V VREF2 = 85 0.895 V VREF2 = 85 0.906 V VREF2 = 86 0.916 V VREF2 = 87 0.927 V Mean noise value Threshold dispersion Parameter dependency compatible with previous measurements (one half of the chip seems to be sensitive to the parameter value)

  10. Vref2 parameter scan Chip D1 (parameter scan) VREF2 = 81 0.887 V VREF2 = 82 0.898 V VREF2 = 83 0.909 V VREF2 = 84 0.920 V VREF2 = 85 0.931 V (@ ICLPDISC = 80) Mean noise value Threshold dispersion Parameter dependency compatible with previous measurements (one half of the chip seems to be sensitive to the parameter value)

  11. Summary • Uniformity of discriminator transfer functions has been studied • Using external reference voltages • External reference voltage doesn’t change measured offsets or noise • With external bias traces removed • Removing external reference voltage traces doesn’t change measured offsets or noise • Trying to use optimization steps proposed by IPHC • Performance dependency on VREF2 similar to what has been observed for other parameters (ICLPDISC, IBufBias, IPIX) • Lower ICLIPDISC = less dispersion

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