1. Noise estimation for the strip readout channel on layer 0 to 5 of the SuperB SVT
L. Ratti
Università degli Studi di Pavia
INFN Pavia
SuperB TDR phone meeting, 18/03/2011

2. Model of the charge measuring system
reset network
CD=detector capacitance+strays
RS=series resistance of the detector CF
shaper
CF=feedback capacitance
Cin=input capacitance
T(stp) es en 1
tp=peaking time
detector RS
T(stp)=shaper transfer function
Q d
charge preamplifier CD
Cin
In a charge sensitive amplifier (CSA), noise performance are mostly dependent on the input device noise features
Noise in the detector leakage current and in the reset network not considered

3. Noise model: preamplifier input device
reset network
CD=detector capacitance+strays
RS=series resistance of the detector CF
shaper
CF=feedback capacitance
Cin=input capacitance
T(stp)
detector es en 1
tp=peaking time RS
T(stp)=shaper transfer function
Q d
charge preamplifier CD
Cin
series 1/f noise
technology dependent contribution
both kf and αf depend on the polarity of the DUT (af,s=0.85 for NMOS, 1.05÷1.2 for PMOS)
series white noise
channel thermal noise
Kf 1/f noise parameter
αf slope-related parameter
kB Boltzmann’s constant
T absolute temperature
αw excess noise coefficient
γ channel thermal noise coefficient
n proportional to the subthreshold ID-VGS slope
gm transconductance
IEEE TNS, vol 54,  no. 3  Jun. 2007, pp

4. thermal noise in the distributed series resistance of the strips
Noise model: strip series resistance
reset network
CD=detector capacitance+strays
RS=series resistance of the detector CF
shaper
CF=feedback capacitance
Cin=input capacitance
T(stp) es en 1
tp=peaking time
detector RS
T(stp)=shaper transfer function
Q d
charge preamplifier CD
Cin
thermal noise in the distributed series resistance of the strips

5. Equivalent noise charge
The ENC expression is as follows
PA input device
strip resistance
where
A1 and A2(af) are shaping coefficients
Cin and Sw depend on input device bias condition, dimensions and polarity
Af depends only on gate dimensions in NMOS devices; it depends also on bias conditions in PMOS devices
1/f noise contribution to the ENC is peaking time dependent

6. ENC contribution from RS
Layer
RS (f) [W]
CD [pF]
57* 9* 1
214
21.5 2
260 26 3
382
38.3 4
292
43.8 5
375
56.3
* including fanout contribution
RC2CR shaping

7. ENC contribution from the PA input device
RC2CR shaping
Example: ENC optimized with respect to input device channel width and relevant optimum W value as a function of the peaking time for CD=9 pF (SVT layer 0)

8. ENC estimate
Layer
CD [pF]
tp [ns]
ENC from RS [e rms]
ENC [e rms]
Channel width [mm]
Hit rate/strip [kHz]
Efficiency 1/(1+N)
9.0 25
180
580
1270
2060
0.890 1
21.5 50
600
1060
272
268
0.969 2
26.0
800
1290
3050
162
0.981 3
38.3
1430
1980
3820
95.7
0.989 4
43.8
1000
310
730
10000
21.9
0.950 5
56.3
450
900
11900
28.1
0.937
RC2CR shaping, ID=500 mA (current in the PA input device), L=200 nm, N-channel input device, analog dead time=2.4 tp

9. ENC estimate
Layer
CD [pF]
tp [ns]
ENC from RS [e rms]
ENC [e rms]
Channel width [mm]
Hit rate/strip [kHz]
Efficiency 1/(1+N)
9.0 25
180
530
1510
2060
0.890 1
21.5 50
600
990
3270
268
0.969 2
26.0
800
1200
3670
162
0.981 3
38.3
1430
1870
4640
95.7
0.989 4
43.8
1000
310
700
11250
21.9
0.950 5
56.3
450
860
13650
28.1
0.937
RC2CR shaping, ID=800 mA, L=200 nm, N-channel input device, analog dead time=2.4 tp

10. ENC estimate
Layer
CD [pF]
tp [ns]
ENC from RS [e rms]
ENC [e rms]
Channel width [mm]
Hit rate/strip [kHz]
Efficiency 1/(1+N) 2
26.0 50
800
1290
3050
162
0.981
100
570
1000
3810
0.963
200
400
790
4700
0.928 3
38.3
1430
1980
3820
95.7
0.989
1010
1490
4810
0.978
720
1150
6020
0.956
RC2CR shaping, ID=500 mA, L=200 nm, N-channel input device, analog dead time=2.4 tp

11. ENC estimate
Layer
CD [pF]
tp [ns]
ENC from RS [e rms]
ENC [e rms]
Channel width [mm]
Hit rate/strip [kHz]
Efficiency 1/(1+N) 4
43.8
1000
310
730
10000
21.9
0.950
800
360
780
9470
0.960
500
450
890
8360
0.974 5
56.3
900
13650
28.1
0.937
520
970
11200
0.949
660
1040
9850
0.967
RC2CR shaping, ID=500 mA, L=200 nm, N-channel input device, analog dead time=2.4 tp

12. Proposed layer grouping (updated rates for L1-L5)
CD [pF]
available tp [ns]
selected tp [ns]
ENC from RS [e rms]
ENC [e rms]
Channel width [mm]
Hit rate/strip [kHz]
Efficiency 1/(1+N)
11.2
25, 50, 100, 200 25
220
740
3000
2060
0.890 1
26.7
100
460
940
697
0.857 2
31.2
590
1100
422
0.908 3
34.4
200
410
325
0.865 4
52.6
400, 600, 800, 1000 (or 500 and 1000)
500
490
1000
9000 47
0.947
600
440
0.937 5
67.5
800
560
1090 28
0.949
1030
RC2CR shaping, ID=500 mA, L=200 nm, N-channel input device, analog dead time=2.4 tp