Analog-to-Digital Converter with Redundancy for Image Sensor Readout

摘要

Methods and systems for analog-to-digital conversion applicable to an image sensor, such as a CMOS image sensor, in which an ADC comprises built-in redundancy such that the ADC can start its conversion cycle before the ADC input settles to a desired resolution and the ADC can yet accurately convert the ADC input to a digital value with the desired resolution. In a CMOS image sensor, such an ADC configuration enables the pixel readout time to overlap with the ADC conversion time, reducing the total time needed to convert the pixel signal value to a digital value with the desired resolution.

主权项

1. An image sensor comprising:
an array of pixels; and at least one analog-to-digital converter (ADC) configured for converting an analog pixel signal corresponding to photocarriers accumulated by a given selected pixel of the pixel array into an N bit digital signal, each said at least one analog-to-digital converter, comprising: an input configured to sample the analog pixel signal; conversion circuitry configured (i) to begin analog-to-digital conversion of the analog pixel signal at said input prior to the analog pixel signal settling to within N-bit resolution, and (ii) to correct the analog-to-digital conversion for error caused by the analog-to-digital conversion beginning prior to the analog voltage input signal settling, such that the analog-to-digital conversion provides an output digital signal that accurately represents the analog voltage signal within N-bit resolution.