A kind of image sensor readout circuit and readout method using improved gain ADC

Abstract

An ADC with increased gain disclosed in the present invention includes a gain amplification unit, a comparator and a counter, wherein the gain amplification unit includes a sampling circuit and a switched capacitor amplifying circuit, and the switched capacitor amplifying circuit includes a capacitor C1, a capacitor C2, Switch K r and the amplifier, wherein the first input terminal of the amplifier is connected to the reference signal, and the second input terminal of the amplifier is simultaneously connected to the sampling capacitor C1, the sampling capacitor C2 and the switch K r One end of the sampling capacitor C1 is connected to the sampling circuit, the sampling capacitor C2 and the switch K r The other end of the amplifier is connected to the output end of the amplifier, the output end of the amplifier is connected to a comparator, and the output end of the comparator is connected to a counter. The invention provides an image sensor readout circuit and readout method using an ADC with increased gain, so that the final image noise level is low, and the dynamic range and signal-to-noise ratio are improved, thereby improving the image quality of the image sensor under low illumination.

Description

technical field [0001] The invention relates to the field of image sensors, in particular to an image sensor readout circuit and a readout method using an ADC with increased gain. Background technique [0002] CMOS Image Sensors (CIS) have been widely used in imaging fields such as video, surveillance, industrial manufacturing, automobiles, and home appliances. The structure of the CIS mainstream readout circuit is based on the column-level single-slope analog-to-digital converter (SS-ADC). The function of the SS-ADC is to compare the signal to be quantized with a ramp reference signal. The result of the comparison is The final quantization is performed by a counter to obtain an N-bit binary digital quantity. Generally, in a traditional readout circuit, the output of the pixel unit is compared with a reference ramp (RAMP) signal input to the comparator, and the output judgment result of the comparator is used as an indication for the ADC counter to stop counting to ensure c...

AI Technical Summary

Problems solved by technology

However, under low illumination, the original signal amplitude is small and the noise level is relatively high. The digital gain Dv multiplies all the noise (image noise and ADC noise), which degrades the CIS image quality.

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