A 32×32 CMOS image sensor: Tested using process and temperature compensated voltage controlled current source

A 32×32 CMOS image sensor is presented. Sensor uses adaptive integration time for every pixel. By cyclically selecting the row, the brighter pixel value is marked and readout first. The dimmer pixel continued to be integrated until its value falls under window defined by two threshold values. To increase throughput and hence to reduce roll time, multiple channels are being used. A PT compensated voltage controlled current source is designed to mimic the behavior of photodiode and the entire sensor was tested. The designed current source produces 1pA to 510pA of current in order to characterize the photodiode of type n+/p substrate of size 5μm×3μm. The current source with a nominal current of 260pA shows a standard deviation of 21.4% and temperature variation of 609 ppm/°C. Entire design is carried out in 1P6M, 180nm standard CMOS process. The designed image sensor used for star tracking.