A Low-Power DROIC With Extended-Counting ADC for Uncooled Infrared Silicon Diode Detectors

A low-power digital readout integrated circuit (DROIC) for silicon diode uncooled infrared focal plane arrays (IRFPAs) is presented. The DROIC adopts a 14-bit column-level extended-counting analog-to-digital converter (ADC) based on a cascade of a coarse continuous-time $\Sigma $ - $\Delta $ ADC and a fine single-slope ADC. While the weak detector signal is integrated, the coarse conversion is implemented by a feedback current-steering digital-to-analog converter (IDAC), which shortens the signal chain and reduces the bandwidth requirement for the op-amp, to reduce power consumption. Besides, the ramp signal of the fine conversion is generated locally by an additional column-level IDAC, which matches the coarse conversion IDAC to decrease the DNL. Also, a low-power non-uniformity calibration circuit is adopted to compensate the non-uniformity of the IRFPA and adjust the ADC’s input signal range. The DROIC with 1024 $\times $ 768 pixel array is fabricated in a $0.18~\mu \text{m}$ CMOS process. The experimental results demonstrate the DROIC consumes 109mW. The noise is 1.7LSB and the equivalent input noise voltage of the column circuit is about $2.1~\mu \text{V}$ rms. The INL and DNL are less than +6.1LSB/−4.4LSB and +0.40LSB/−0.38LSB, respectively.