Transcript Document

MGPA status
Mark Raymond (4/9/02)
Conclusion from preliminary study (July 02)
Design which meets spec. looks feasible
Design progress since July
More realistic design now under simulation
complete chip, all 4 channels simultaneously
all transistor model (Ideal current sources/sinks now real components)
can identify and eliminate/overcome any undesirable inter-channel effects
transistor dimensions for much of design now at or close to final
RAL meeting (1st Aug.) M.French, L.Jones
Technical discussion on design and layout issues
no major problems identified
layout to begin ~ end Sept (Lawrence Jones)
Lawrence to look after I2C interface and bias generator circuitry
Areas still needing attention
Noise
highest gain channel (0 – 2pC, 0 – 50GeV) meets spec. with margin
lower gain -> higher noise as V/I resistor increases (non-negligible noise contribution) (only recently perceived as problem)
one solution is to redistribute gains between V/I and diff O/P Stages
reduce Rvi -> lower noise but higher gain -> compensate by
reducing diff O/P gain (currently 9)
=> all channels no longer identical on chip (probably not an issue?)
All simulations to date for nominal process parameters – need to simulate process variation effects on performance
Transmission line effects between APD and MGPA?
Power supply rejection
Target package -> may affect layout (common solution with ADC?)
ADC interface & coupling CM level (need more dedicated meeting)
………
Sept, 2002
CMS Ecal
1
V/I gain
resistors
CSA
external
components
define CR
offset
adjust
external
components
define RC
source
followers
Sept, 2002
transconductance
stage V/I
CMS Ecal
Bias
generation
I2C
interface
2
Pulse shapes: (out+) – (out-)
highest gain (0 -> 2pC, 0 -> 50 GeV)
next highest (0 -> 8pC, 0 ->200 GeV)
higher
gain
saturates
linear
range
linear
range
Sept, 2002
CMS Ecal
3
next lowest (0 -> 16pC, 0 -> 400 GeV)
lowest gain (0 -> 60pC, 0 ->1500 GeV)
3 higher
gains
saturate
2 higher
gains
saturate
linear
range
linear
range
Sept, 2002
CMS Ecal
4
linearity
lowest gain
peak pulse heights
linearity [% fullscale]
highest gain
peak pulse heights
fit
linearity [(peak pulse ht. – fit)*100/fullscale]
Sept, 2002
CMS Ecal
5
highest gain range
out +
(out +) – (out -)
linear
range
linear
range
out -
Sept, 2002
CMS Ecal
6