1. Status of the CARIOCA project
Walter Bonivento
CERN / INFN Cagliari
for the LHCb collaboration
and the CERN MIC group

2. W.Bonivento CERN/INFN Cagliari
The LHCb muon detector
LHCb muon detector: main task provide L0 trigger for b   X
Five stations, M1 to M5; four radial regions, R1 to R4
R3-R4 of M4-M5 RPC 48% area
rate cap. 1kHz/cm2
R1-R2 of M t.b.d. 1% area
rate cap. 1MHz/cm2
the rest MWPC 52% area
rate cap. 100kHz/cm2
LEB Stockholm 2001
W.Bonivento CERN/INFN Cagliari

3. Readout electronics for MWPC: a) detector architecture
Main performance requirement:
efficiency in 20ns >99%
2 bi-gap logically OR-ed
(DIALOG chip)
2mm gap, 1.5mm wire spacing
wire, cathode and combined readout
LEB Stockholm 2001
W.Bonivento CERN/INFN Cagliari

4. Readout electronics for MWPC: b) requirements
Detector signal: current with fast (ns) rise, fall
Detector capacitance from 20pF to 200pF
One threshold for time stamping: time resolution from slewing effect
Optimum amplifier peaking time
compromise between
noise and slewing
LEB Stockholm 2001
W.Bonivento CERN/INFN Cagliari

5. Readout electronics for MWPC: b) requirements
Optimum amplifier peaking time: about 10ns
At large Cdet weak dependence of time resolution on peaking time
To be able to set the threshold at about 6 p.e.
Measurements on a prototype chamber performed with a
hybrid from PNPI and a modified version of ASDQ chip
(M.Newcomer-Penn)
noise <2fC for Cdet pF
At gas gain of 105
average 40fC for wires and 20fC for cathode
range 150fC for 95% of the signals
LEB Stockholm 2001
W.Bonivento CERN/INFN Cagliari

6. Readout electronics for MWPC: b) requirements
High rate: dead time
pulse width <50ns
unipolar and tail cancellation
wire signals AC coupled with RLCdec= 100s
baseline shifts baseline restoration
Low cross-talk : Zin< 50 
LEB Stockholm 2001
W.Bonivento CERN/INFN Cagliari

7. CARIOCA Project overview
80k FE channels at 1Mrad dose in 10 years
custom chip in radiation tolerant technology m CMOS
Final goal: differential structure
Cancels
1/t
tail
Cancels
preamp
tail
LEB Stockholm 2001
W.Bonivento CERN/INFN Cagliari

8. CARIOCA Project overview
PROTOTYPE CHIPS: step by step approach
2000: positive preamp+current discriminator
+LVDS 4ch (1 analog ch.)
2001: positive preamp+current discriminator
+LVDS 14ch
LEB Stockholm 2001
W.Bonivento CERN/INFN Cagliari

9. CARIOCA Project overview
2001: negative preamp 8ch analog
2001: positive preamp+shaper 4ch analog (diff. out.)
2001: positive preamp+shaper+voltage discriminator+LVDS 4ch (diff. out.)
2002: positive and negative full chain with baseline restorer (diff.out.)
LEB Stockholm 2001
W.Bonivento CERN/INFN Cagliari

10. The positive preamplifier: a) design
Current amplifier NMOS with current mode feedback; unipolar
Large input transistor
W/L=1600m/0.7m
Id=2mA
at about 20MHz, the other two at
150MHz and 300MHz
Dominant pole
Followed by current discriminator (presented at LEB2000 by D.Moraes
and replaced by a voltage discriminator in next version) +LVDS driver
LEB Stockholm 2001
W.Bonivento CERN/INFN Cagliari

11. The positive preamplifier: b) measurements
Digital (S-curve)...
...and analog measurements
Linearity
Response to a delta
Sensitivity: 8mV/fC (measurement)
LEB Stockholm 2001
W.Bonivento CERN/INFN Cagliari

12. The positive preamplifier: b) measurements
Response to a delta
Threshold
vs.Cd
Noise vs. Cd
ENC = 867e- + 36e-/pF
Channel uniformity of noise and threshold: 7% r.m.s.
Cross talk around 1%
Power consumption of about 18mW per channel dominated by
LVDS driver
Analog measurement
Digital measurement
Simulation (CADENCE)
calculation from noise
theory
LEB Stockholm 2001
W.Bonivento CERN/INFN Cagliari

13. The positive preamplifier: b) measurements
Problems of the discriminator:
1) it does not work below 10fC (need 5fC).
It was tested on a chamber prototype
efficiency plateau shifted by 100V w.r.t. to
our best measurement (with ASDQ chip).
2) it slows down the signal rise-time significantly (input C of discr.)
Peaking time
vs.Cd
7ns are expected from p.a. alone
Discriminator changed
in next versions of the chip
LEB Stockholm 2001
W.Bonivento CERN/INFN Cagliari

14. The negative preamplifier: a) design
N2,N3,N4 replaced by PMOS
LEB Stockholm 2001
W.Bonivento CERN/INFN Cagliari

15. The negative and positive preamp: frequency response
CADENCE simulation
positive
Closed loop gain
3dB level is at:
16 MHz for negative
23 MHz for positive
Cdet=60pF
Input impedance: below 50
LEB Stockholm 2001
W.Bonivento CERN/INFN Cagliari

16. The negative preamplifier: b) measurements
Response to a delta
Cd=15pF
Cd=100pF
Linearity
Measurements
Simulation
LEB Stockholm 2001
W.Bonivento CERN/INFN Cagliari

17. The negative preamplifier: b) measurements
Response to a delta
Peaking time vs. Cd
improved w.r.t first
prototype
Sensitivity vs. Cd
Noise vs. Cd
ENC= 951e- + 31e-/pF
Channel uniformity of noise and threshold: 7% r.m.s.
Measurements
Simulation
LEB Stockholm 2001
W.Bonivento CERN/INFN Cagliari

18. The negative preamplifier: b) measurements
Response to a quasi 1/t pulse
Cd=15pF
Cd=100pF
quasi 1/t injector
LEB Stockholm 2001
W.Bonivento CERN/INFN Cagliari

19. W.Bonivento CERN/INFN Cagliari
The shaper: a) design
Folded cascode fully differential balanced (CMF)
Designed for 1ns peaking time (not to add to the preamp)
Dominant pole (neglecting p.z. comp)
at 160MHz
LEB Stockholm 2001
W.Bonivento CERN/INFN Cagliari

20. W.Bonivento CERN/INFN Cagliari
The shaper: a) design
2-pole/zero network to compensate for the 1/t tail
basic idea from R.A.Boie et al.,NIM 192(1982)365
adapted to a differential amplifier design (M.Newcomer, Penn)
Cdet=60pF
LEB Stockholm 2001
W.Bonivento CERN/INFN Cagliari

21. The shaper: b) measurements
This prototype chip with the positive preamplifier
Response to a delta: single ended ouptut (true output will be differential)
Cd=15pF
Cd=100pF
LEB Stockholm 2001
W.Bonivento CERN/INFN Cagliari

22. The shaper: b) measurements
Response to a delta: single ended output (true output will be differential). Saturation current on ( ) and off ( )
Measurements
Simulation
Linearity: improved with saturation current ON (changes the DC level at the drain of N0)
LEB Stockholm 2001
W.Bonivento CERN/INFN Cagliari

23. The shaper: b) measurements
Response to a delta: single ended output (true output will be differential). Saturation current on.
Cd=100pF
Cd=15pF
LEB Stockholm 2001
W.Bonivento CERN/INFN Cagliari

24. The shaper: b) measurements
Response to a delta: single ended output
Sensitivity vs. Cd
Peaking time vs. Cd.
Faster than negative
consistent with different
bandwidth
ENC= 1290e- + 40e-/pF
with saturation current ON
Noise vs. Cd
Parallel noise term higher than
preamp alone due to two
preamplifiers at shaper input
Measurements
Simulation
LEB Stockholm 2001
W.Bonivento CERN/INFN Cagliari

25. The shaper: b) measurements
Response to a quasi 1/t pulse
Cd=100pF
Cd=15pF
LEB Stockholm 2001
W.Bonivento CERN/INFN Cagliari

26. The shaper: b) measurements
Response to a quasi 1/t pulse
Peaking time vs. Cd
Measurements
Simulation
Sensitivity vs. Cd
Pulse width vs. Cd
LEB Stockholm 2001
W.Bonivento CERN/INFN Cagliari

27. Conclusions and perspectives
Negative preamplifier and positive preamplifier with shaper
chips tested and satisfying the requirements for LHCb operation
Amplifier+shaper+Voltage discriminator chip (following ATLAS MDT chip design) under test
+Baseline restoration chip under design
LEB Stockholm 2001
W.Bonivento CERN/INFN Cagliari

28. THE END