1. Readout Electronics for Pixel Sensors
Integrating ASICs for Scintillator-coated X-ray pixel sensors.
Integrating ASICs for Ion beam profiling.
Pixel electronics for photon counting.
Platform meeting
June 11, Sundsvall
Sensor Technology Group
Munir A. Abdalla

2. ASICs for scintillator-coated X-ray pixel sensor
Pixel sensor based on p-diffusion/n-well photodiode with in-pixel preamplifier (NIM-A)
Improved optical sensitivity.
Low direct X-ray absorption.
Phototransistor-based pixel sensor, (IEEE ICECS’2k1)
Cancellation of the dark current was achieved.
Work should be done to improve the FPN.
Monte Carlo simulation of imaging properties, (NSS’2000).
Platform meeting
June 11, Sundsvall
Sensor Technology Group
Munir A. Abdalla

3. ASICs for Ion Beam Profiler
A pixel array readout electronics was fabricated and tested.
10x10 array size.
520x520 um pixel size.
Chip size 6.5x6.5 mm2 .
Current integrating mode.
A new version with improvements includes:
Variable dynamic range by multiple divisions of the input current.
Improved output current readout with a transistor switch.
A 400 pixel array will be assembled.
Platform meeting
June 11, Sundsvall
Sensor Technology Group
Munir A. Abdalla

4. Sensor Technology Group
ASICs for Ion Beam Profiler
Microphotograph of part of the chip showing some pixels and bonding pads
Chip photograph of the ion beam ASIC
Platform meeting
June 11, Sundsvall
Sensor Technology Group
Munir A. Abdalla

5. Sensor Technology Group
Pixel detector for Ion Beam Profiler
Sequence of images showing the ion beam moving across the graphite detector. The data was taken by the ASIC chip.
A photograph of the graphite detector mounted to the flange
Platform meeting
June 11, Sundsvall
Sensor Technology Group
Munir A. Abdalla

6. Pixel Electronics for Photon Counting
A new biasing method for preamplifier-shapers, (IEEE ICECS’2k).
An all-analogue time-walk free SCA for photon counting pixel sensors, (WSES/IEEE CSCC’2k1)
An All-digital window discriminator, (IEE Letters)
Low digital interference counter for photon counting pixels.
Platform meeting
June 11, Sundsvall
Sensor Technology Group
Munir A. Abdalla

7. A new biasing method for preamplifier-shapers
CMOS technology is attractive in ASICs.
CSA is widely used in front-end electronics for radiation detectors.
For a good noise performance Rf must be very high (Mega/Giga Ohm).
MOS transistor Mf is operated in the linear or subthreshold range to reach high Rds values.
A special bias for Mf is required. Mf Rf Cf
Vout
Iin
- A
Platform meeting
June 11, Sundsvall
Sensor Technology Group
Munir A. Abdalla

8. Sensor Technology Group
Circuit Description Rf
If A >> (Ci + Cf) /Cf
Vout = - A Vin
= - A . Q /(Ci + (A+1)Cf)
or:
Vout = - Q / Cf Cf
- A
Vin
Vout Ci
Simplified charge-sensitive amplifier (CSA) configuration.
Platform meeting
June 11, Sundsvall
Sensor Technology Group
Munir A. Abdalla

9. Sensor Technology Group
Circuit Description
Charge-sensitive preamplifier
differentiation
Nth order integration
Amplification Rf Cf
- A
-A1
-A2
-An Cd
Pole-zero cancellation
detector
General analog pulse processing channel
Platform meeting
June 11, Sundsvall
Sensor Technology Group
Munir A. Abdalla

10. Sensor Technology Group
Circuit Description
The CSA circuit and the feedback bias scheme
Platform meeting
June 11, Sundsvall
Sensor Technology Group
Munir A. Abdalla

11. Sensor Technology Group
Circuit Description
A block diagram of the CSA-shaper showing the mirror bias circuit
Platform meeting
June 11, Sundsvall
Sensor Technology Group
Munir A. Abdalla

12. Sensor Technology Group
Circuit Description
A schematic diagram of the CSA-shaper showing the mirror bias circuit
Platform meeting
June 11, Sundsvall
Sensor Technology Group
Munir A. Abdalla

13. Sensor Technology Group
Simulation Results
The temperature range represent threshold variations.
CSA output at - 65 oC
CSA output at 25 oC
The CSA output response for a charge pulse (0.1 fC) at various temperatures (- 65 oC to 25 oC).
Platform meeting
June 11, Sundsvall
Sensor Technology Group
Munir A. Abdalla

14. Sensor Technology Group
Simulation Results
Shaper output at -30 oC
Shaper output at 45 oC
The output shaped pulse at various temperatures (-30 oC to 45 oC) .
Platform meeting
June 11, Sundsvall
Sensor Technology Group
Munir A. Abdalla

15. Sensor Technology Group
Simulation Results
The output of the shaper’s first stage at different values of an external control current . The longer shaping time corresponds to the lower current value.
Platform meeting
June 11, Sundsvall
Sensor Technology Group
Munir A. Abdalla

16. Sensor Technology Group
Simulation Results
The shaper output for different control current values showing a tuneable gain.
Platform meeting
June 11, Sundsvall
Sensor Technology Group
Munir A. Abdalla

17. Sensor Technology Group
Simulation Results
Rds.Cf time constant
increases for lower values of Is
The CSA output for various feedback resistor values (Rds controlled by the current source Is)
Platform meeting
June 11, Sundsvall
Sensor Technology Group
Munir A. Abdalla

18. Sensor Technology Group
Simulation Results
Shaper output for
various Rds values
Higher and lower Rds
(CSA output)
The output pulse shape is fixed regardless of the value of the feedback resistor, Rds.
Platform meeting
June 11, Sundsvall
Sensor Technology Group
Munir A. Abdalla

19. An all-analogue SCA for photon counting pixels
Schematic diagram of the all-analog SCA
Platform meeting
June 11, Sundsvall
Sensor Technology Group
Munir A. Abdalla

20. An all-analogue SCA for photon counting pixels
A complete schematic diagram of the all-analog SCA
Platform meeting
June 11, Sundsvall
Sensor Technology Group
Munir A. Abdalla

21. Sensor Technology Group
Conclusions
The scintillator-coated pixel sensor using a p-diff/n-well photosensor with an in-pixel preamplifier has the best performance (good sensitivity and low noise).
The ASIC chip for ion beam profiling will be modified to allow a flexible dynamic range by employing a current gain control. A better output current readout control will be implemented.
Circuit mirroring is an efficient method for achieving a stable operation of MOS transistors in the non-saturation mode by providing respectively adaptive nodes that vary in the same manner as the main circuit.
Platform meeting
June 11, Sundsvall
Sensor Technology Group
Munir A. Abdalla

22. Sensor Technology Group
Conclusions
An all-analog pixel design would result in a reduced pixel size and low electronic noise. It will also result in a higher readout speed since the serial data shifting of the traditional in-pixel counter is eliminated.
The implementation of an asynchronous design of the window discriminator logic will achieve an overall area-efficient photon counting pixel..
The design of a prescaled shift-counter in a photon counting pixel significantly reduces the noise caused by the switching activity of the digital part in the pixel circuit.
Platform meeting
June 11, Sundsvall
Sensor Technology Group
Munir A. Abdalla