Current Input Extended Counting ADC With Wide Dynamic Range for LWIR FPAs

A readout circuit incorporating a pixel level analog-to-digital converter (ADC) is studied for 2-D long wavelength infrared focal plane arrays (LWIR FPAs). The charge handling capacity of the unit cell circuit is improved by using the current input incremental ADC. The proposed pixel level ADC is based on an extended counting ADC but is composed of two oversampling conversions. The readout circuit has been fabricated using a 0.35 mum 2-poly 4-metal CMOS process for a 128 times 128 LWIR HgCdTe array with a pixel size of 50 mum times 50 mum. The peak signal-to-noise ratio (S/N) and dynamic range (DR) were measured to be 85.8 dB and 99.9 dB, respectively, with a total power consumption of 50 mW.