A Fast Correlated Multiple Sampling Method Combined with Two-step ADC

Abstract

A fast correlation multi-sampling method combined with two-step ADC, adopting single-slope ADC to perform single quantization to obtain high-order digital output, and adopting successive approximation and comparison ADC to perform repeated quantization to obtain low-order digital output; the present invention consists of a sample-and-hold circuit, SS It is composed of ADC, voltage storage unit, adder, SAR ADC and accumulation and averaging circuit; this method greatly reduces the number of clock cycles required for readout compared with the traditional correlation multiple sampling method; combining SS ADC and SAR ADC, utilizing the area The smaller but slower SS ADC performs a single coarse quantization, and the larger but faster SAR ADC is used for repeated fine quantization, which avoids the problem of a significant increase in the area of ​​the DAC array caused by only using the SAR ADC for quantization , and avoid the problem that the repeated quantization of the SS ADC seriously slows down the readout speed.

Description

technical field [0001] The invention relates to the design field of analog integrated circuits, in particular to a fast correlation multiple sampling method combined with a two-step ADC. Background technique [0002] Low-noise image sensors can provide high imaging quality in low-light environments, and meet the application requirements of medical imaging, security monitoring and other fields. [0003] Correlated multiple sampling (CMS) can effectively suppress the noise of the image sensor. Traditional correlated multiple sampling circuits such as figure 1 , consists of a sample-and-hold circuit, an analog-to-digital converter (Analog to Digital Converter, ADC), a switch, an adder, and a memory. In the traditional correlation multiple sampling process, the digital output of all bits of the ADC is quantized multiple times, so M times of sampling and quantization are performed, and the noise voltage is theoretically reduced times, but the readout time will be increased by...

AI Technical Summary

Problems solved by technology

[0005] In order to overcome the deficiencies in the prior art, the present invention proposes a fast correlation multiple sampling method combined with a two-step ADC to solve the problem that in the traditional correlation multiple sampling method, the readout time of the image sensor increases proportionally with the increase of sampling and quantization times. Large size, which severely limits the readout speed of the image sensor, and it is difficult to achieve a compromise between the readout speed and area of ​​the sensor based on a single ADC-based correlation multiple sampling method

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