A 14-bit differential-ramp single-slope column-level ADC for 640×512 uncooled infrared imager

Abstract

This paper presents a low-power 14-bit column-level ADC for 640×512 size uncooled infrared imager. A novel differential-ramp single-slope (DRSS) structure is proposed in this work, which achieves 2x faster conversion speed and 3dB higher SNR performance compared with classical single-slope scheme. Moreover, a novel low-power area-saving result-consistent coarse-fine TDC scheme is proposed. The sensor with 17μm pixel pitch has been realized in 0.5 μm 2P3M CMOS process and applied in the thermal imaging system. Power consumption of per ADC is 120 μW. Measurement results demonstrate an average output RMS noise of 0.5LSB and a maximum nonlinearity of 3LSB.