Quick correlation multiple sampling method combined with two-step ADC

Abstract

The invention relates to a quick correlation multi-sampling method combined with a two-step ADC. Single quantization by using a monoclinic ADC is performed to obtain high-order digital output, and repeated quantization is performed by using a successive approximation comparison ADC to obtain low-order digital output; and the circuit of the method is composed of a sample hold circuit, an SS ADC, avoltage storage unit, an adder, an SAR ADC and an accumulation and average circuit. Compared with a traditional correlation multi-sampling method, the method has the advantages that the clock period number required by reading is greatly reduced; and the SS ADC and the SAR ADC are combined, the SS ADC with a small area and a low speed is used to carry out single coarse quantization, and the SAR ADCwhich is large in area and high in speed is used for repeated fine quantization, so the problem that the area of a DAC array is remarkably increased due to the fact that only SAR ADC quantization isadopted is solved, and the problem that the reading speed is severely decreased due to the fact that SS ADC quantization is adopted for repeated quantization is also solved.

Description

technical field [0001] The present invention designs the field of analog integrated circuit design, and in particular relates 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 are suitable for applications in medical imaging, security monitoring and other fields. [0003] Correlated multiple sampling (CMS) can effectively suppress the noise of image sensors. Traditional correlated multiple sampling circuits such as figure 1 , consisting 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 multi-sampling process of correlation, 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 inc...

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

Images