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)

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)

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)

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)

Readout electronics goals Low noise: Photometry: 2.8e rms (9.8mV) @100kHz Large dynamic range: 96dB from noise floor to 130ke well depth (16-bit) Readout frequency: 100 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)

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

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

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)

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)

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

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

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

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

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)

Power consumption Bandgap Reference  0.86 mW Reference Buffer  11.29 mW ADC  22.84 mW Preamp/Integrator  31.55 mW Total power less than 17 mW/channel 1/12/2019 Armin Karcher (LBNL)

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)

AC Coupling performance No observable change in gain - DC coupled: Gain = 3.5919 µV/ADU - AC coupled: Gain = 3.5916 µV/ADU No change in noise 1/12/2019 Armin Karcher (LBNL)

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

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)

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)

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)

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)