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AIDA design review Davide Braga Steve Thomas ASIC Design Group 11 March 2008

AIDA design review Davide Braga Steve Thomas ASIC Design Group 11 March 2008. Overview. Noise consideration Time jitter Intermediate Energy Channel Crosstalk Continuous reset feedback Slew-rate limited configuration Low Frequency Feedback Loop. Noise Analysis.

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AIDA design review Davide Braga Steve Thomas ASIC Design Group 11 March 2008

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  1. AIDA design review Davide Braga Steve Thomas ASIC Design Group 11 March 2008

  2. Overview • Noise consideration • Time jitter • Intermediate Energy Channel • Crosstalk • Continuous reset feedback • Slew-rate limited configuration • Low Frequency Feedback Loop

  3. Noise Analysis Noise vs. shaping time, detector leakage current: Idet=1nA, 10nA Idet=1nA Idet=10nA Noise [μV] Noise [μV] 205 150 2 1.75 shaping Time [μs] shaping Time [μs]

  4. Noise Analysis Noise vs. shaping time, detector leakage current: Idet=100nA, 1μA →Idet must be < 100nA (detector cooling?) Idet=100nA Idet=1μA Noise [mV] Noise [μV] 325 0.5 2 0.25 2 shaping Time [μs] shaping Time [μs]

  5. Time Jitter Output preAmplifier [V] [μs] • Comparator with hysteresis from previous design • Transient noise simulation with multiple noise seeds

  6. Time Jitter Jitter rms [s] Comparator threshold=0.26% FSR

  7. Intermediate Energy Channel preAmplifier Output Cf=30pF → decreases with Cf Cf=0.6pF [V] Cf=30pF preAmplifier modified to increase slew rate in order to limit input voltage spikes time [μs]

  8. Crosstalk Fast collection time increases crosstalk Simulation with 3 adjacent channels

  9. Crosstalk • Coupling capacitance adjacent channels: Ccoupl=58pF • → Considerable response even in the third channel • (but different peaking time: this may be used to discriminate spurious signals) • (see “AIDA Technical Specification”, pag.17) input voltage shaper output

  10. Crosstalk • Adjacent channel response < 0.25% FSR • →Ccoupl<2pF 2nd channel shaper output Ccoupl=58pF Ccoupl=2pF

  11. Continuous Reset System Vbias W W*N • Shaper and preAmplifier have different input references • →M1-M2 don’t match,usual pole-zero cancellation doesn’t work M1 M2 Rf Cf Cf*N -A -A Vref_amp Vref_sh • - a non-inverting shaper with time-constant of ~1μs would allow the use of a common reference, but would discharge the preamp’s output too quickly • - Using the pulsed reset, which is needed anyway for short dead time, would work without p-z canc.

  12. Slew-rate limited reset configuration • The source is towards the input side to fix the operating point • This is not possible if the leakage current is in the opposite direction of the signal current! Vref_amp Ibias (see S.Thomas, “AIDA amplifier feedback options” 20/02/07) Ileak -A S=0.1V D=[0.1:1.6]V S=1.6V D=[1.6:0.1]V VdsP>0! VdsN<0! Ileak Ileak Isig Isig

  13. Slew-rate limited reset configuration • If the leakage current has the same polarity of the signal: • pMOS feedback transistor: linearity ~=0.4% • nMOS feedback transistor: linearity ~=0.015% (Linearity improves for the Medium Energy Channel)

  14. Low Frequency Feedback Loop reset configuration • This architecture works with both leakage current polarities • Linearity: 0.6% 0.4 -0.2 Input current [μA]

  15. Issues • Detector current critical for noise • Important to limit interstrip capacitance between adjacent channels • Leakage current polarity is important in designing preamplifier’s feedback

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