AIDA design review

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

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Overview

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

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Noise Analysis
Noise vs. shaping time, detector leakage
current Idet1nA, 10nA
Idet1nA
Idet10nA
Noise µV
Noise µV
205
150
2
1.75
shaping Time µs
shaping Time µs
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Noise Analysis
Noise vs. shaping time, detector leakage
current Idet100nA, 1µA ?Idet must be lt 100nA
(detector cooling?)
Idet100nA
Idet1µA
Noise mV
Noise µV
325
2
2
0.25
0.5
shaping Time µs
shaping Time µs
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Time Jitter
Output preAmplifier
V
µs
Comparator with hysteresis from previous
design Transient noise simulation with multiple
noise seeds
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Time Jitter
Jitter rms s Comparator threshold0.26 FSR
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Intermediate Energy Channel
preAmplifier Output
Cf30pF ? decreases with Cf
Cf0.6pF
V
Cf30pF
preAmplifier modified to increase slew rate in
order to limit input voltage spikes
time µs
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Crosstalk
Fast collection time increases crosstalk Simulati
on with 3 adjacent channels
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Crosstalk
Coupling capacitance adjacent channels Ccoupl58p
F ? 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
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Crosstalk
Adjacent channel response lt 0.25 FSR ?
Ccoupllt2pF
2nd channel shaper output
Ccoupl58pF
Ccoupl2pF
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Continuous Reset System
Vbias
W
WN
Shaper and preAmplifier have different input
references ? M1-M2 dont match, usual pole-zero
cancellation doesnt work
M1
M2
Rf
Cf
CfN
-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 preamps output too
quickly - Using the pulsed reset, which is
needed anyway for short dead time, would work
without p-z canc.
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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
S0.1V
D0.11.6V
S1.6V
D1.60.1V
VdsPgt0!
VdsNlt0!
Ileak
Ileak
Isig
Isig
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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)

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Low Frequency Feedback Loop reset configuration
This architecture works with both leakage current
polarities Linearity 0.6
0.4
-0.2
Input current µA
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Issues

• Detector current critical for noise
• Important to limit interstrip capacitance between
  adjacent channels
• Leakage current polarity is important in
  designing preamplifiers feedback