1. Turning photons into bits in the cold
Integrated signal processing and A/D conversion in one focal plane mounted ASIC
Turning photons into bits in the cold
1/12/2019
Armin Karcher (LBNL)

2. Overview What is the CRIC 2 chip ? Why did we build it ?
How does it work ?
Multi slope integrator
ADC
Test results
Linearity
Noise
Cross-talk
Power consumption
AC-coupling
Cold performance
Where we go from here
Conclusion
1/12/2019
Armin Karcher (LBNL)

3. CRIC 2: 4 Channel CCD readout
Pre-Amp CDS Multi-slope
13 Bit ADC
Logic
I/O
Voltage Reference
1/12/2019
Armin Karcher (LBNL)

4. Why did we build it?
The CRIC 2 chip is part of a fully-integrated detector readout system for the proposed SNAP space telescope.
Integrating many detectors on a passively cooled focal plane strongly favors local readout with a micro-power ASIC.
1/12/2019
Armin Karcher (LBNL)

5. Readout electronics goals
Low noise: Photometry: 2.8e rms
Large dynamic range: 96dB from noise floor to 130ke well depth (16-bit)
Readout frequency: kHz & 50kHz
Radiation tolerant: 10 kRad ionization (well shielded)
Low power: ≈ 200mJ/image/channel ≈ 10mW/channel
Operation at 140K and 300K Allow normal operation at 140K and chip testing at room temperature
Compact
Robust, space qualified
1/12/2019
Armin Karcher (LBNL)

6. Signal Path Voltage Reference Auto Gain Multi Slope Pipeline ADC
1/12/2019
Armin Karcher (LBNL)

7. Multi Slope Integrator
1/12/2019
Armin Karcher (LBNL)

8. Multi Slope Integrator
>16 bits of dynamic range with 13 bit ADC
Large signals are Poisson noise dominated
Charge is conserved (no offset)
Gain calibration at 3 points fully characterizes the system.
1/12/2019
Armin Karcher (LBNL)

9. ADC design Pipeline architecture Low power High resolution Compact
12 identical stages minimize layout effort
All capacitor design is radiation tolerant
1/12/2019
Armin Karcher (LBNL)

10. Integral Nonlinearity
1/12/2019
Armin Karcher (LBNL)

11. Integral Nonlinearity
deviation from line fit
Note:
1 LSB ≈ 1e- ≈ 3.5 mV
1/12/2019
Armin Karcher (LBNL)

12. Differential Nonlinearity
1/12/2019
Armin Karcher (LBNL)

13. Noise Gain 32: Multislope dominated noise
Less than 1 bit RMS ADC noise !
Gain 1
1/12/2019
Armin Karcher (LBNL)

14. Crosstalk Crosstalk of less than 2 ADU for a full-scale signal.
This is at the measurement limit of our system.
1/12/2019
Armin Karcher (LBNL)

15. Power consumption Bandgap Reference  0.86 mW
Reference Buffer  mW
ADC  mW
Preamp/Integrator  mW
Total power less than 17 mW/channel
1/12/2019
Armin Karcher (LBNL)

16. AC Coupling Vref ClampR 200KW Chip input To CCD output stage On/off
amplifier
On/off
C=1uF
Clamp
Vref
Clamp is on during start up (CCD power up) to charge C, off afterwards.
During normal operation:
ClampR is closed only during the CCD reset level integration.
On/off is closed only during CCD reset and video level integration.
1/12/2019
Armin Karcher (LBNL)

17. AC Coupling performance
No observable change in gain
- DC coupled:
Gain = µV/ADU
- AC coupled:
Gain = µV/ADU
No change in noise
1/12/2019
Armin Karcher (LBNL)

18. Voltage Reference Only 7mV variation in voltage during cooldown
1/12/2019
Armin Karcher (LBNL)

19. Cold Performance Noise at 298K: 2.23ADU Noise at 153K: 1.90ADU
Noise reduction of ~15%
Gain increase of ~5%
1/12/2019
Armin Karcher (LBNL)

20. Outlook
Integration of digital control and timing is in process. Look for the CRIC3 chip next spring.
Radiation testing is planned for this summer.
A clock driver and bias generator chip (CLIC) is being developed to create a fully integrated focal plane readout system.
1/12/2019
Armin Karcher (LBNL)

21. CLIC chip in development
0V, 80V adj (Vsub dc)
-5V, +15V adj (V clk)
-5V, +10V adj (TG clk)
Power supply
(4V?)
-5V, +10V adj (H clk)
CLIC
0V, +5V adj (Output gate dc)
-8V, +8V adj (SW clk)
-8V, 0V adj (Reset gate clk)
-15V, 0V adj (Reset drain dc)
Input clock
-25V,0 DC adj (Output drain dc)
Config. data
-20V,0 DC (p+ guard dc)
3.3V/2.5V (Analog/Dig) CRIC dc
1/12/2019
Armin Karcher (LBNL)

22. Conclusion Linearity is ~3.5µV (1 ADU) RMS
6.5µV cold noise is well below system goal
Excellent crosstalk: -95dB
The CRIC2 CCD readout chip meets all design requirements!
1/12/2019
Armin Karcher (LBNL)