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

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