A multipurpose circuit to read out and digitize pixel signal for low-power CMOS imagers

A complementary metal oxide semiconductor (CMOS) image sensor with a resolution of 128 × 128 pixels is presented in this paper in which pixel signal readout, noise suppression, and comparing operations are performed by one circuit during two steps: reading and conversion. The main idea of this work is to combine three main operations of an image sensor in one circuit. This method helps to decrease power consumption, silicon area, total noise, and imaging time. The total power consumption of the imager is 11 mW with a 2.5-V power supply and 40-fps frame rate. The pixel layout size is 10 × 10 μm² with a fill-factor of 81%. The analog to digital converter (ADC) resolution is 10 bits, and the error resulted from the proposed circuit is about ±0.5 least significant bit (LSB). The proposed CMOS image sensor was designed based on Taiwan Semiconductor Manufacturing Company (TSMC) 0.18-μm CMOS technology and was simulated by CADENCE SPECTRE circuit simulator. This circuit can be proposed for a CMOS imager with highly accurate and efficient power consumption.