A Low-Noise Dynamic Comparator with Offset Calibration for CMOS Image Sensor Architecture

Abstract

A low-noise, high-speed, low-input-capacitance switched dynamic comparator (SDC) CMOS image sensor architecture is presented in this paper. The comparator design occupying less area and consuming lesser power is suitable for bank of comparators in CMOS image readouts. The proposed dynamic comparator eliminates the stacking issue related to the conventional comparator and reduces the offset noise further. The need for low-noise, low-power, area-efficient and high-speed flash analog-to-digital converters (ADCs) in many applications today motivated us to design a comparator for ADC. The rail-to-rail output swing is also improved. The input capacitance is reduced by using shared first-stage technique. The comparator is designed with constant [Formula: see text]/[Formula: see text] biasing to suppress the environmental drift. The simulation results from 45-nm and 65-nm CMOS technologies confirm the analysis results. It is shown that in the proposed dynamic comparator both the power consumption and delay time are significantly reduced. The maximum clock frequency of the proposed comparator can be increased to 3.5[Formula: see text]GHz and 2.2[Formula: see text]GHz at supply voltages of 1[Formula: see text]V and 0.6[Formula: see text]V, respectively. Simulations are carried out using predictive technology models for 45[Formula: see text]nm and 65[Formula: see text]nm in HSPICE.