1. FEE2006 - Perugia. A. Rivetti A FAST LARGE DYNAMIC RANGE SHAPING AMPLIFIER FOR PARTICLE DETECTOR FRONT-END A.Rivetti – P Delaurenti INFN – Sezione di Torino

2. FEE2006 - Perugia. A. Rivetti Project framework  Development of a fast binary read-out chip for Compass at CERN  Chip designed to replace an older ASIC (MAD4) in the RICH upgrade  User requirements:  Preserve the compatibility with the existing read-out  Reduced gain for MPT read-out  Threshold adjustable channel by channel  Hit rate > 5 MHz  Power consumption < 30 mW/channel  From 0.8 um BiCMOS to 0.35 um CMOS

3. FEE2006 - Perugia. A. Rivetti ASIC overview  Variable gain front-end  Fast comparator  8 bit DAC  Programmable one shot  LVDS driver  LDO

4. FEE2006 - Perugia. A. Rivetti Front-end building blocks  Variable gain preamp  Rail-to-rail output shaper  Continuous-time baseline restorer

5. FEE2006 - Perugia. A. Rivetti A typical core amplifier  Commonly used in preamp and shapers  Source follower has limited swing  Asymmetrical slew-rate

6. FEE2006 - Perugia. A. Rivetti Example of slew-rate requirements Vout (V) dt  Fast shaping time require slew rates of the order of 100 V/  s.  Example: 2.5 V @ 10 ns peaking time requires 400 V/  s.  Particularly critical if off-chip loads have to be driven.  In class A, for 10pF 4mA of bias current dV (V/sec) time (s)

7. FEE2006 - Perugia. A. Rivetti Better output stages Vout Vin Vbias Zero Vt devices!  Very simple  Class AB  Requires special devices  No rail-to-rail (V ds,sat +V TH )  Rail-to-rail  More complex class AB control  No special devices  rail-to-rail (2V ds,sat ) Vout

8. FEE2006 - Perugia. A. Rivetti Class AB control circuit D. M. Montecelli, IEEE JSSC, Vol. SC-21, Dec. 1986 Hogervost et al., IEEE JSSC Vol. 29, No. 12, Dec. 1994. Vout Vin1 Vin2 IB/2IB IB/2  Minimum current 0.3 Iq  Maximum current >> Iq

9. FEE2006 - Perugia. A. Rivetti Complete op-amp

10. FEE2006 - Perugia. A. Rivetti Simulated slew-rate performance Output pulse with 10pF load (blue curve) and 100pF output load time (s) Output voltage (Volt)

11. FEE2006 - Perugia. A. Rivetti Pulse shape tuning Output voltage (Volt) time (s) Output pulse with 10pF load and reduced compensating capacitors

12. FEE2006 - Perugia. A. Rivetti Critical components

13. FEE2006 - Perugia. A. Rivetti From the literature (1)

14. FEE2006 - Perugia. A. Rivetti From the literature (2)

15. FEE2006 - Perugia. A. Rivetti BLH block diagram - + Vref_OTA Vout Vref_BLR From preamp - + Closed loop buffer with slew rate limitation Gm stage Class AB OTA

16. FEE2006 - Perugia. A. Rivetti Behavioral simulation  Optimization driven by an analytical model of the full chain in Mathematica  SR limitation modelled in the time domain

17. FEE2006 - Perugia. A. Rivetti Full circuit model  Analytical model of the full chain to simulate accurately baseline shifts

18. FEE2006 - Perugia. A. Rivetti Baseline drift with Gm-stage only Analytical model Baseline drift smaller owing to SR limitation in the Gm-stage (not modelled) Spice simulation Simulation with random arrival time

19. FEE2006 - Perugia. A. Rivetti Effect of the buffer With SR-limited buffer-Spice Analytical model with SR-limited Buffer (zoom around baseline) Without SR-limited buffer-Spice

20. FEE2006 - Perugia. A. Rivetti Gm-stage schematic Vbias Vin 1 Vin 2 Iout

21. FEE2006 - Perugia. A. Rivetti SR-limited buffer schematic

22. FEE2006 - Perugia. A. Rivetti BLR layout 400  m 200  m

23. FEE2006 - Perugia. A. Rivetti First prototype results Linearity Peaking time ENC 1450 e-@10pF Credits due to Michela Chiosso for the tests of the chip!

24. FEE2006 - Perugia. A. Rivetti Exploring the critical region 0 fC 900 fC

25. FEE2006 - Perugia. A. Rivetti “Curiosity driven” simulations in 0.13  m Same class AB topology scaled down to 0.13  m and powered at 1.2 V

26. FEE2006 - Perugia. A. Rivetti Pulse shape with 10 pF and 100 pF loads 10 ns 810 mV 12 ns 895 mV  10 pF output load  100 pF output load R2/R1=4 Csh=240 fF power = 800  W

27. FEE2006 - Perugia. A. Rivetti Linearity in 0.13  m

28. FEE2006 - Perugia. A. Rivetti Low voltage class AB control Vout Vin 1 Vin 2 K. J. de Langen, J. H. Huijsing. IEEE JSSC, Vol. 33, No. 10, Oct. 1998.