Performance of Sidecar Hawaii2RG

As illustrated in the block diagram in Fig. 1, a complete detector system consisting of the SIDECAR ASIC and the HAWAII-2RG multiplexer has been assembled. The HAWAII-2RG, hybridized to a short-wave infrared detector with 2.5 ^m cutoff frequency, was mounted next to the ASIC inside the dewar and was operated in unbuffered mode. The SIDECAR ASIC was programmed to generate the required bias voltages and clock signals. At the same time, the SIDECAR digitized the four analog FPA outputs at 100 kHz pixel rate and sent the digital data to the host PC.

Figure 5 shows a full field CDS frame with a total noise of 16 e-. This is comparable to or better than results obtained with a conventional discrete controller system. To demonstrate suitability for the JWST instruments, the total noise was measured for a Fowler-8 sampling scheme (NIRCam) and for the sampling-up-the-ramp scheme with 22 groups of 4 averaged frames (NIRSpec). The gray-scale images and the corresponding histograms are shown in Fig. 6. All JWST noise requirements have been met with margin.

Figure 5. CDS frame acquired by the SIDECAR ASIC shows 16 e- noise.

Figure 6. (top) Fowler 8-8 over a 1000s integration yields a total noise of 6.5 e--,

(bottom) sampling-up-the-ramp over 1000s integration yields a total noise of 5 e-.

Figure 6. (top) Fowler 8-8 over a 1000s integration yields a total noise of 6.5 e--,

(bottom) sampling-up-the-ramp over 1000s integration yields a total noise of 5 e-.

Besides noise performance, power consumption is important in many cryogenic detector systems. For JWST, a total budget of less than 10 mW has been allocated for each 2K*2K detector to allow for passive radiative cooling. Table 2 summarizes the measured power consumption for all contributors inside the SIDECAR and the HAWAII-2RG. A total power of 9.4 mW has been demonstrated.

Table 2. Power consumption for operation with 4 channels including H2RG detector.

Component

Power Consumption

HAWAII-2RG

0.4 mW

16-bit ADCs (4 channels)

5.2 mW (1.3 mW / channel)

Preamplifiers (4 channels)

1.0 mW (0.25 mW / channel)

Bias generator

1.2 mW

Micro-controller & Clocking

1.5 mW

LVDS Driver

0.1 mW

Total Power

9.4 mW

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