Sidecar Asic

JWST's near-IR SCAs will be controlled using Rockwell's SIDECAR ASIC (see Fig. 14). The SIDECAR generates all clocks and low-noise biases needed by the SCA, performs pre-amplification and 16-bit ADC conversion, and executes data conditioning and transmission to ISIM data systems. Prior to selecting the SIDECAR, the JWST project reviewed all aspects of the ASIC design. During this review, the SIDECAR demonstrated outstanding performance, exceeding JWST specification in important areas including total noise for NIRSpec (see Fig. 15).

Figure 14. Rockwell's SIDECAR ASIC will be used for near-IR FPA control and readout.

Rockwell Scientific Self-reported Measurements

Noise at low bias1

Noise at medium bias1

JWST Requirement

ASIC by itself (NIRSpec 4-22 multiaccum)

2.0 e-

1.8 e-

2.4 e-(NIRSpec)



16.5 e-

16.2 e-3

24 e-(extrapolated)

ASIC + HAWAII-2RG Fowler 8-8

6.8 e-

6.7 e-

9 e-(NIRCAM)

ASIC + HAWAII-2RG <4 -22 multiaccum)

5.3 e-

5.2 e-2'3


'100 kHz pixel rate

1MULTI ACCUM-22x4 calculated using 4 out of 6 measured ramps due to larger frame-to-frame pedestal in remaining 2 ramps.

^Analysis of test data independently confirmed by NASA/GSFC

Figure 15. Prior to baselining the SIDECAR ASIC, the JWST Project reviewed its readiness.

Rockwell's self-reported measurements met JWST requirements for parameters, including noise. Independent analysis of the data by GSFC confirmed important results including total noise <6 e- rms in the NIRSpec readout mode.

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