Column readout circuit for CMOS image sensor

Abstract

The invention discloses a column readout circuit for a CMOS image sensor. The circuit comprises a programmable gain amplifier for converting a single-end unipolar signal into a double-end bipolar signal, and a differential input two-step successive approximation analog-to-digital converter (SAR ADC), wherein a pixel point output voltage can be converted into the double-end bipolar signal through the programmable gain amplifier adopting the time-division and block-division sampling technology and the switch capacitor level transition technology, so that a dynamic signal range can be enlarged; and the double-end bipolar analog signal output by the programmable gain amplifier can be converted into a digital signal through the small-area differential input two-step SAR ADC, and the digital signal can be supplied to an imaging device. Therefore, the column readout circuit for the CMOS image sensor has the characteristics that a large dynamic range and a high frame frequency can be achieved.

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

Images