A column readout circuit applied to cmos image sensor

Abstract

The invention discloses a column readout circuit applied to a CMOS image sensor, which comprises a programmable gain amplifier for converting a single-end unipolar signal to a double-end bipolar signal and a differential input two-step successive approximation analog-to-digital converter. The circuit uses a programmable gain amplifier with time-division and block sampling and switched capacitor level shifting technology to convert the pixel output voltage into a double-ended bipolar signal with a larger amplitude to improve the dynamic range of the signal; The stepwise successive approximation analog-to-digital converter converts the double-terminal bipolar analog signal output by the programmable amplifier into a digital signal, which is provided to the imaging device. Therefore, the column readout circuit of the present invention is applied to a CMOS image sensor, which can realize the characteristics of large dynamic range and high frame rate.

Description

technical field [0001] The invention belongs to the technical field of integrated circuit design, and in particular relates to a column readout circuit applied to a CMOS image sensor. Background technique [0002] With the continuous development of CMOS technology, the application range of CMOS image sensors is becoming more and more extensive because of its low power consumption, simple power supply, high integration, and low cost. With the continuous improvement of imaging quality requirements, the number of pixels and frame frequency of image sensors continue to increase, and higher requirements are placed on the accuracy and speed of the matching readout circuit. Therefore, it is important to improve the dynamic range and conversion frequency of the readout circuit. Technical problems that image sensor technology must solve. Under the existing technical conditions, the readout circuit is divided into a global readout circuit, a column readout circuit and a pixel point r...

AI Technical Summary

Problems solved by technology

(3) The analog-to-digital converter converts the analog output voltage of the programmable gain amplifier into a digital quantity twice successively, and finds the difference between the two to provide to the imaging device. Each pixel signal sampling requires two analog-to-digital conversions Converter transition time, limiting the overall frame rate

To sum up, the single-ended structure column readout circuit is limited by the structure itself, and it is difficult to achieve wide dynamic range and high frame rate characteristics

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