Correlated double sampling circuit, analog to digital converter and image sensor including the same

Patent metadata

Field	Value
Publication number	US-9538111-B2
Application number	US-201414527049-A
Country	US
Kind code	B2
Filing date	Oct 29, 2014
Priority date	Dec 26, 2013
Publication date	Jan 3, 2017
Grant date	Jan 3, 2017

Abstract

An image sensor includes a sampling circuit, which is responsive to ramp and input signals provided by a pixel array. The sampling circuit is configured to perform a correlated double sampling (CDS) operation on a reset component of the input signal and an image component of the input signal. A reset circuit is also provided, which is configured to reset an output signal generated by the sampling circuit to a first level in response to a reset control signal. This reset control signal can be active during at least one of a first reset interval and a second reset interval. The first reset interval precedes a first comparison interval during which a first comparison operation is performed on the ramp signal and the reset component. The second reset interval precedes a second comparison interval during which a second comparison operation is performed on the ramp signal and the image component.

First claim

What is claimed is:

1. An integrated circuit device, comprising:
a sampling circuit comprising a comparator having a first input terminal connected to a ramp signal, a second input terminal connected to an input signal from an image-sensor pixel array and an output terminal, the sampling circuit configured to perform a correlated double sampling (CDS) operation on a reset component of the input signal and an image component of the input signal; and
a reset circuit having a first terminal connected to a reference signal and a second terminal connected to the output terminal of the comparator, the reset circuit configured to provide an output signal at the output terminal of the comparator with a first voltage in response to a reset control signal, which is active during at least one of a first reset interval and a second reset interval, said first reset interval preceding a first comparison interval during which a first comparison operation is performed on the ramp signal and the reset component, and said second reset interval preceding a second comparison interval during which a second comparison operation is performed on the ramp signal and the image component,
wherein the reset control signal is inactive during the first comparison interval and during the second comparison interval.

2. The integrated circuit device of claim 1 , wherein said comparator comprises a differential amplifier having a first input connected to the ramp signal and a second input connected to the input signal.

3. The integrated circuit device of claim 2 , wherein a node of the differential amplifier is electrically connected to a pull-up bias circuit or a pull-down bias circuit.

4. The integrated circuit device of claim 1 , further comprising an auto-zero switch connected to the output terminal of the sampling circuit and the second input terminal of the sampling circuit, the auto zero switch configured to turn on by an auto zero control signal during an auto-zero time interval, which precedes the first comparison interval.

5. The integrated circuit device of claim 2 , wherein the input signal is provided to a node that is capacitively coupled to the second input terminal of the comparator.

6. The integrated circuit device of claim 1 , further comprising a digital signal generation circuit configured to perform a digital conversion operation on the output signal.

7. An analog to digital converter (ADC) comprising:
a correlated double sampling (CDS) circuit configured to sample an input signal to generate an output signal, the input signal being provided from a pixel array; and
a digital signal generation unit configured to perform a digital conversion operation on the output signal to generate a digital signal, wherein the CDS circuit comprises:
a sampling unit configured to perform a CDS operation on a reset component of the input signal and an image component of the input signal based on a ramp signal and configured to generate the output signal;
an output reset unit configured to reset the output signal to a level of a reference voltage provided to the output reset unit based on a reset control signal which is activated during at least one of a first reset interval and a second reset interval, the first reset interval preceding a first comparison interval in which a first comparison operation is performed on the ramp signal and the reset component, the second reset interval preceding a second comparison interval in which a second comparison operation is performed on the ramp signal and the image component; and
an auto-zero switch configured to connect the output signal and the input signal by an auto zero control signal during an auto-zero time interval, which precedes the first comparison interval,
wherein the output reset unit includes a reset switch that connects the reference voltage to an output node during at least one of the first and second reset interval,
wherein the reset control signal is inactive during the first comparison interval and during the second comparison interval.

8. The ADC of claim 7 , wherein the sampling unit includes a comparator that compares the ramp signal and the input signal to provide the output signal at the output node.

9. The ADC of claim 7 , wherein the digital signal generation unit includes a counter that counts an input clock signal based on the output signal to generate the digital signal during each of the first and second comparison intervals.

10. The ADC of claim 7 , wherein the digital signal generation unit includes a latch circuit that latches a counter clock signal based on the output signal to generate the digital signal during each of the first and second comparison intervals.

11. An image sensor comprising:
a pixel array including a plurality of unit pixels configured to sense an incident light to generate pixel signals corresponding to the incident light;
a correlated double sampling (CDS) block configured to perform CDS operation on the pixel signals to generate output signals; and
a digital signal generation unit configured to perform digital conversion operation on the output signals to generate digital signals corresponding to the output signals,
wherein the CDS block includes a plurality of CDS circuits, each connected to each column line of the pixel array, and each of the CDS circuits includes:
a sampling unit configured to perform a CDS operation on a reset component of the pixel signal and an image component of the pixel signal based on a ramp signal and configured to generate the output signal; and
an output reset unit configured to reset the output signal to a level of a reference voltage based on a reset control signal which is activated during both of a first reset interval and a second reset interval, the first reset interval preceding a first comparison interval in which a first comparison operation is performed on the ramp signal and the reset component, the second reset interval preceding a second comparison interval in which a second comparison operation is performed on the ramp signal and the image component,
wherein the output reset unit includes a reset switch that connects the reference voltage to an output node during both of the first and second reset interval, and
wherein the reset control signal is inactive during the first comparison interval and during the second comparison interval.

12. The image sensor of claim 11 , wherein the sampling unit includes a comparator that compares the ramp signal and the pixel signal to provide the output signal at the output node.

13. The image sensor of claim 11 , wherein the digital signal generation unit includes a plurality of counters, each connected to each of the CDS circuits and each of the counters counts an input clock signal based on the output signal to generate the digital signal during each of the first and second comparison intervals.

14. The image sensor of claim 13 , further comprising:
a control unit that provides the input clock signal to the counters.

15. The image sensor of claim 11 , wherein the digital signal generation unit includes a plurality of latch circuits, each connected to each of the CDS circuits and each of the latch circuit latches a counter clock signal based on the output signal to generate the digital signal during each of the first and second comparison intervals.

16. The image sensor of claim 15 , further comprising:
a global counter that generates the counter clock signal to the latch circuits.

17. The integrated circuit device of claim 1 , wherein the reference voltage has a level of a power supply voltage or a ground voltage.

Assignees

• Yang Han
• Lee Kwang-Hyun
• Samsung Electronics Co Ltd

Inventors

• Yang Han
• Lee Kwang-Hyun

Classifications

• H04N25/616 Primary

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

• H04N25/67

  applied to fixed-pattern noise, e.g. non-uniformity of response · CPC title

• H04N25/78

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

• H04N5/378 Primary

  Electricity · mapped topic

• H04N5/365

  Electricity · mapped topic