A Power-Efficient CMOS Active Pixel Sensor Imager with Column-Level Difference ADC in 0.18-μm

In this paper a CMOS active pixel sensor (APS) imager with column-level analog-to-digital converter (ADC) is presented. In conventional column-level ADC imagers, the ADCsare active in the entire readout time intervals. But by using difference ADCs where the difference of consecutive samples isdigitized instead of each sample independently, and by noting the fact that the light intensity of neighbouring pixels in a column are usually very close, the single-slope ADCs digitizing thedifferences are not active in the entire readout intervals leading to considerable saving the power consumption. According tosimulation results of the circuit in a 0.18-μm CMOS technology, the proposed imager with 30x40 pixel array and with 8-bitcolumn-level ADCs and 130 frame/s, consumes 830μW where the power consumption of the ADCs and the entire imager are reduced by factors of 10 and 2, respectively

Keywords:

Active pixel sensor (APS) , Analog to digital converter (ADC) , Integrating , Single-slope