A Comparison of Imaging Subsystems for Analog- versus Digital-Output Detector Arrays

Infrared CMOS detector arrays are key to scientific imaging, including Earth remote sensing, astronomy, and planetary exploration. Even as more digital functions are incorporated into CMOS readout integrated circuits—first, with digital-to-analog bias generation and later, with analogto- digital conversion of the pixel readout—external electronics are still needed to supply these devices with low-noise power and provide suitable data interfaces. This paper describes two implemented designs for such electronics, one for an analogoutput detector array, and one for a digital-output array. Both subsystems are intended for planetary infrared imaging spectrometers and output data with similar frame sizes, rates, and bit depth. They include DC-DC conversion from bus power, connection to the detector array through a rigid-flexible printed circuit, data buffering and output through SpaceWire, and commanding over a UART. Due to their similarities in scope and capability, it is meaningful to compare the resources needed by each subsystem. We find that digital-output detectors minimize subsystem mass and volume, but analog-output detectors minimize subsystem power and heat rejection needs. Other tradeoffs are also discussed.