A Gain-Adaptive Single-Slope ADC Employing Column Lateral Capacitors for CMOS Image Sensors

A novel high dynamic range high speed column parallel single-slope ADC for CMOS image sensors is proposed. A gain adaptive structure is realized employing column lateral capacitors. With the help of a configurable up/down counter, this structure is compatible with dual correlated double sampling (CDS) scheme which acquires a capability of high noise suppression with no additional memories used. The nonlinearity of the proposed ADC is within 0.73% without extra calibration. Compared with conventional single-slope ADCs, the gain adaptive ADC extends dynamic range by 12dB in the same conversion time.