A 128-Stage Analog Accumulator for CMOS TDI Image Sensor

The impacts of parasitic phenomenon on the performance of the analog accumulator in CMOS TDI image sensor are analyzed in this paper, and a modified accumulator with decoupling capacitor Cd to combat the parasitic phenomenon is also proposed. A 128-stage modified accumulator is designed and simulated. A prototype 1024 × 128 CMOS TDI image sensor with the 128-stage modified accumulator is fabricated in 0.18- μm one-poly four-metal 1.8 V/3.3 V CMOS technology. With a line rate of 3875 lines/s, at 128 stages the measured sensitivity and SNR improvement of the fabricated sensor are 617.1 V/lux·s and 16.6 dB respectively. The simulation and experiment results have proved the effectiveness of the decoupling capacitor C_d when combating the parasitic phenomenon in the analog accumulator. The proposed modified accumulator is suitable for application in CMOS TDI image sensor with high stages.