US 2022/0103768 A1Published application

Image sensor having high resolution analog to digital converter

AssigneeShenzhen Goodix Technology Co., Ltd.

InventorsChao YANG, Matthew POWELL

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Abstract

An image sensor includes ADCs, each including a comparator receiving a ramp signal and an image signal, and generating a comparator output. Each ADC also includes a counter ceasing to change a digital count value in response to a change in the comparator output. The digital count value has a first resolution. Each ADC also includes a delay line circuit including a delay line generating a first digital value encoding a duration of a period of the counter clock and generating a second digital value encoding a first portion of the period of the counter clock. Each ADC also includes a delay to digital circuit generating a digital output value based on the first and digital values. The digital output value encodes a second value of the ramp signal, where the digital count value has a second resolution that is greater than the first resolution.

Claims20

Dependent claims

An image sensor, comprising:

a plurality of image sensor cells, each configured to generate an image signal;
and
a plurality of analog to digital converters (ADCs), each configured to receive the image signal of one of the image sensor cells, wherein each ADC comprises:
a comparator configured to receive a ramp signal and the image signal of one of the image sensor cells, and to generate a comparator output signal indicating whether the ramp signal is greater than the image signal,
a counter configured to change a digital count value in response to a counter clock signal, and configured to cease changing the digital count value in response to a change in the comparator output signal, wherein the digital count value encodes a first analog value of the ramp signal, and wherein the digital count value has a first resolution,
a delay line circuit comprising one or more delay lines, wherein the delay line circuit is configured to generate a first digital value encoding a duration of a period of the counter clock signal and to generate a second digital value encoding a first portion of the period of the counter clock signal, and
a delay to digital circuit configured to generate a digital output value based on the first digital value and the second digital value, wherein the digital output value encodes a second value of the ramp signal, wherein the digital count value has a second resolution, and wherein the second resolution is greater than the first resolution.

4 more elements

A method of using an image sensor, the method comprising:

with each of a plurality of image sensor cells, generating an image signal;
with each of a plurality of analog to digital converters (ADCs), receiving the image signal of one of the image sensor cells;
with a comparator of a particular ADC, receiving a ramp signal and the image signal of one of the image sensor cells;
with the comparator, generating a comparator output signal indicating whether the ramp signal is greater than the image signal;
with a counter of the particular ADC, changing a digital count value in response to a counter clock signal, wherein the digital count value encodes a first analog value of the ramp signal, and wherein the digital count value has a first resolution;
with the counter, in response to a change in the comparator output signal, ceasing to change the digital count value;
with a delay line circuit of the particular ADC, generating a first digital value encoding a duration of a period of the counter clock signal;
with the delay line circuit, generating a second digital value encoding a first portion of the period of the counter clock signal;
and
with a delay to digital circuit of the particular ADC, generating a digital output value based on the first digital value and the second digital value, wherein the digital output value encodes a second analog value of the ramp signal, wherein the digital count value has a second resolution, and wherein the second resolution is greater than the first resolution.

7 more elements

Dependencies are inferred from the claim text.