Image sensor and analog to digital converter and analog to digital converting method thereof

Patent metadata

Field	Value
Publication number	US-9712772-B2
Application number	US-201414459654-A
Country	US
Kind code	B2
Filing date	Aug 14, 2014
Priority date	Aug 14, 2013
Publication date	Jul 18, 2017
Grant date	Jul 18, 2017

Abstract

An image sensor is provided. The image sensor includes a pixel array having active pixel sensors arranged in rows and columns; a correlated double sampler that converts sensing signals transferred from pixels sensors selected from the active pixel sensors to correlated double sampling signals and outputs a conversion result by column; and an analog-to-digital converter that converts the correlated double sampling signals corresponding to plural columns to digital signals using a global code. The analog-to-digital converter includes a column shared operator that performs a digital conversion operation on correlated double sampling signals corresponding to two or more columns of the plural columns.

First claim

What is claimed is:

1. An image sensor comprising:
a pixel array having a plurality of active pixel sensors arranged in rows and columns;
a correlated double sampler configured to convert sensing signals transferred from pixel sensors selected from the plurality of active pixel sensors to correlated double sampling signals and to output a conversion result by column; and
an analog-to-digital converter configured to convert the correlated double sampling signals corresponding to a plurality of columns to digital signals using a global code,
wherein the analog-to-digital converter comprises a column shared operator that performs an arithmetic logic operation on a correlated double sampling signal set in a time division manner for two or more of the plurality of columns.

2. The image sensor of claim 1 , wherein each of the correlated double sampling signals comprises a sampling value of a reference signal sensed under a condition where a light is not incident on the pixel sensor, and an image signal sensed under a condition where a light is incident on the pixel sensor.

3. The image sensor of claim 2 , wherein the column shared operator is implemented by a subtractor that subtracts a global code value corresponding to the reference signal and the image signal of each of the two or more columns, through a logical operation.

4. The image sensor of claim 1 , wherein the column shared operator comprises:
a multiplexer configured to select one of the two or more columns; and
an adder-subtractor configured to perform an addition or subtraction operation on a reference code and an image code of the column selected by the multiplexer.

5. The image sensor of claim 4 , further comprising:
a latch unit configured to latch the reference code and the image code from a correlated double sampling signal corresponding to each column using the global code.

6. The image sensor of claim 4 , wherein the adder-subtractor sequentially performs the addition or subtraction operation on the reference code and the image code with respect to the two or more columns.

7. The image sensor of claim 4 , wherein the adder-subtractor adds 2's complement of the reference code and the image code.

8. The image sensor of claim 4 , wherein the adder-subtractor subtracts the reference code from the image code.

9. The image sensor of claim 1 , wherein the analog-to-digital converter comprises:
a ramp signal generator configured to generate a ramp signal for converting a level of the correlated double sampling signals to time-axis length information;
a plurality of comparators configured to compare the ramp signal with the correlated double sampling signals respectively corresponding to the plurality of columns;
a global counter configured to generate the global code, the global code being up-counted at the same time with a decrease in the ramp signal; and
a latch unit configured to latch a global code value corresponding to each column in response to a transition of an output voltage of each comparator.

10. The image sensor of claim 9 , further comprising:
a timing controller configured to control a time point when the ramp signal generator generates the ramp signal and a time point when the global counter generates the global code.

11. An analog-to-digital converting method of an image sensor which converts a plurality of correlated double sampling signals sensed from a plurality of active pixel sensors in a correlated double sampling manner to image data, the method comprising:
comparing the plurality of correlated double sampling signals with a ramp signal;
generating a global code provided in common to each of the plurality of columns, the global code being up-counted or down-counted;
latching the global code corresponding to each column according to a result of comparing of the plurality of correlated double sampling signals and the ramp signal to acquire a reference code and an image code corresponding to each column; and
performing an arithmetic operation on the reference code and the image code corresponding to each column using an adder-subtractor shared by two or more columns in a time-division manner and generating image data corresponding to each column.

12. The analog-to-digital converting method of claim 11 , wherein the generating image data corresponding to each column comprises:
selecting the reference code and the image code corresponding to a first column of the plurality of columns to be provided to the adder-subtractor; and
selecting the reference code and the image code corresponding to a second column of the plurality of columns to be provided to the adder-subtractor.

13. The analog-to-digital converting method of claim 11 , further comprising:
sequentially storing image data of each column in a column memory corresponding to each column.

14. An analog-to-digital converting method of an image sensor comprising a plurality of analog-to-digital converters which convert signals sensed from a plurality of pixel sensors to digital image data, the method comprising:
selecting pixel sensors of the plurality of pixel sensors;
converting sensing signals transferred from the selected pixel sensors to correlated double sampling signals by column;
converting the correlated double sampling signals corresponding to a plurality of columns to digital signals using a global code;
and performing an arithmetic logic column shared operation on a correlated double sampling signal set in a time division manner for two or more of the plurality of columns.

Assignees

• Kim Jinwoo
• Kim Kyung-Min
• Lee Jungho
• Chae Heesung
• Jung Seunghoon
• Samsung Electronics Co Ltd

Inventors

• Kim Jinwoo
• Kim Kyung-Min
• Lee Jungho
• Chae Heesung
• Jung Seunghoon

Classifications

• H04N25/616 Primary

  involving a correlated sampling function, e.g. correlated double sampling [CDS] or triple sampling · CPC title

• H04N5/378 Primary

  Electricity · mapped topic

• H04N5/3575

  Electricity · mapped topic

• H04N5/357

  Electricity · mapped topic

• H04N25/78 Primary

  Readout circuits for addressed sensors, e.g. output amplifiers or A/D converters · CPC title