# US 9,438,830 B2 · Analog-to-digital converter and CMOS image sensor including the same

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- Number: US 9,438,830 B2
- Document ID: US9438830B2
- Status: Granted
- Kind: B2
- Application number: 14/491,775
- Filed: 2014-09-19
- Published: 2015-10-01
- Granted: 2016-09-06
- Earliest claimed: 2014-03-28
- Assignees: SK hynix Inc.
- Applicants: SK hynix Inc.
- Inventors: Jin-Seon Kim; Eun-Jun Kim
- Web page: https://patentgrep.com/patent/US9438830B2

## CPC

- H04N 25/616: involving a correlated sampling function, e.g. correlated double sampling [CDS] or triple sampling
- H04N 25/767: Horizontal readout lines, multiplexers or registers
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION

## Abstract

A CMOS image sensor includes an active pixel array suitable for generating an active pixel signal, a dummy pixel array suitable for generating a dummy pixel signal, a row driver suitable for controlling the active pixel array and the dummy pixel array to simultaneously operate at a same column, and a correlated double sampling (CDS) array suitable for generating an active sampling signal and a dummy sampling signal, which are sampled from the active pixel signal and the dummy pixel signal by using a correlated double sampling, respectively, based on a first ramp signal and a second ramp signal, and comparing the active sampling signal with the dummy sampling signal.

## Claims

### Claim 1

An analog-to-digital converter, comprising:
a ramp signal generator suitable for generating a first ramp signal and a second ramp signal; and
a correlated double sampling (CDS) array,
wherein the CDS array includes a CDS circuit at each column, and
wherein the CDS circuit includes:
a dummy sampling signal generation unit suitable for generating a dummy sampling signal, which is sampled from a dummy pixel signal outputted from a dummy pixel array by using a correlated double sampling, based on the first ramp signal;
an active sampling signal generation unit suitable for generating an active sampling signal, which is sampled from an active pixel signal outputted from an active pixel array by using a correlated double sampling, based on the second ramp signal, and
a comparison unit suitable for comparing the dummy sampling signal with the active sampling signal.

### Claim 2 (depends on 1)

The analog-to-digital converter of claim 1, wherein the dummy pixel array includes an optical black (OB) pixel array.

### Claim 3 (depends on 1)

The analog-to-digital converter of claim 1, wherein the dummy sampling signal generation unit and the active sampling signal generation unit have a differential input structure using a same circuit.

### Claim 4 (depends on 1)

The analog-to-digital converter of claim 1, wherein the dummy sampling signal generation unit includes:
a first switch suitable for controlling a transmission of the dummy pixel signal;
a first blocking capacitor coupled between an input node of the first ramp signal and an output node of the first switch; and
a first signal storage capacitor coupled to the output node of the first switch, and suitable for providing the dummy pixel signal.

### Claim 5 (depends on 4)

The analog-to-digital converter of claim 4, wherein the active sampling signal generation unit includes:
a second switch suitable for controlling a transmission of the active pixel signal;
a second blocking capacitor coupled between an input node of the second ramp signal and an output node of the second switch; and
a second signal storage capacitor coupled to the output node of the second switch, and suitable for providing the active sampling signal.

### Claim 6 (depends on 5)

The analog-to-digital converter of claim 5, wherein the first switch and the second switch have a same element, the first blocking capacitor and the second capacitor have a same element, and the first signal storage capacitor and the second signal storage capacitor have a same element.

### Claim 7 (depends on 1)

The analog-to-digital converter of claim 1, wherein the active pixel signal and the dummy pixel signal have a same noise characteristic, and the first ramp signal and the second ramp signal have a same noise characteristic.

### Claim 8 (depends on 1)

The analog-to-digital converter of claim 1, wherein an input of the comparison unit is expressed as,
Vinp−Vinm=(RAMP−RAMP_REF)−(APS_O−OB_O),
where Vinp−Vinm denotes the input of the comparison unit, RAMP denotes the first ramp signal, RAMP_REF denotes the second ramp signal, APS_O denotes the active pixel signal and OB_O denotes the dummy pixel signal.

### Claim 9 (depends on 1)

The analog-to-digital converter of claim 1, wherein the dummy pixel array has a same horizontal characteristic as the active pixel array.

### Claim 10 (depends on 1)

The analog-to-digital converter of claim 1, wherein dummy pixels included in the dummy pixel array are matched one to one with active pixels included in the active pixel array at each column.

### Claim 11

An analog-to-digital converter, comprising:
a correlated double sampling (CDS) array,
wherein the CDS array includes a CDS circuit at each column, and
wherein the CDS circuit includes:
a dummy sampling signal generation unit suitable for generating a dummy sampling signal, which is sampled from a dummy pixel signal outputted from a dummy pixel array by using a correlated double sampling;
an active sampling signal generation unit suitable for generating an active sampling signal, which is sampled from an active pixel signal outputted from an active pixel array by using a correlated double sampling; and
a comparison unit suitable for comparing the dummy sampling signal with the active sampling signal.

### Claim 12 (depends on 11)

The analog-to-digital converter of claim 11, wherein the dummy pixel array includes an optical black (OB) pixel array.

### Claim 13

A CMOS image sensor, comprising:
an active pixel array suitable for generating an active pixel signal;
a dummy pixel array suitable for generating a dummy pixel signal;
a row driver suitable for controlling the active pixel array and the dummy pixel array to simultaneously operate at a same column; and
a correlated double sampling (CDS) array suitable for generating an active sampling signal and a dummy sampling signal, which are sampled from the active pixel signal and the dummy pixel signal by using a correlated double sampling, respectively, based on a first ramp signal and a second ramp signal, and comparing the active sampling signal with the dummy sampling signal.

### Claim 14 (depends on 13)

The CMOS image sensor of claim 13, wherein the dummy pixel array includes an optical black (OB) pixel array.

### Claim 15 (depends on 13)

The CMOS image sensor of claim 13, wherein the CDS array includes a CDS circuit at each column, and
wherein the CDS circuit includes:
a dummy sampling signal generation unit suitable for generating the dummy sampling signal sampled from the dummy pixel signal based on the first ramp signal;
an active sampling signal generation unit suitable for generating the active sampling signal from the active pixel signal based on the second ramp signal; and
a comparison unit suitable for comparing the dummy sampling signal with the active sampling signal.

### Claim 16 (depends on 15)

The CMOS image sensor of claim 15, wherein the dummy sampling signal generation unit and the active sampling signal generation unit include a differential input structure using a same circuit.

### Claim 17 (depends on 15)

The CMOS image sensor of claim 15, wherein an input of the comparison unit is expressed as,
Vinp−Vinm=(RAMP−RAMP_REF)−(APS_O−OB_O),
where Vinp−Vinm denotes the input of the comparison unit, RAMP denotes the first ramp signal, RAMP_REF denotes the second ramp signal, APS_O denotes the active pixel signal and OB_O denotes the dummy pixel signal.

### Claim 18 (depends on 13)

The CMOS image sensor of claim 13, wherein the active pixel signal and the dummy pixel signal have a same noise characteristic, and the first ramp signal and the second ramp signal have a same noise characteristic.

### Claim 19 (depends on 13)

The CMOS image sensor of claim 13, wherein the dummy pixel array is disposed along a row direction to form at least a row and to have a same horizontal characteristic as the active pixel array.

### Claim 20 (depends on 13)

The CMOS image sensor of claim 13, wherein dummy pixels included in the dummy pixel array are matched one to one with active pixels included in the active pixel array at each column.

### Claim 21

A CMOS image sensor, comprising:
an active pixel array suitable for generating an active pixel signal;
a dummy pixel array suitable for generating a dummy pixel signal;
a row driver suitable for controlling the active pixel array and the dummy pixel array to simultaneously operate at a same column; and
a correlated double sampling (CDS) array suitable for generating an active sampling signal and a dummy sampling signal, which are sampled from the active pixel signal and the dummy pixel signal by using a correlated double sampling, respectively, and comparing the active sampling signal with the dummy sampling signal.

### Claim 22 (depends on 21)

The CMOS image sensor of claim 21, wherein the dummy pixel array includes an optical black (OB) pixel array.

### Claim 23 (depends on 21)

The CMOS image sensor of claim 21, wherein the dummy pixel array is disposed along a row direction to have a same horizontal characteristic as the active pixel array.

### Claim 24

A CMOS image sensor, comprising:
an active pixel array suitable for generating an active pixel signal;
a dummy pixel array suitable for generating a dummy pixel signal, wherein the dummy pixel array includes dummy pixels corresponding one to one to active pixels included in the active pixel array at each column;
a row driver suitable for controlling the active pixel array and the dummy pixel array to simultaneously operate at a same column; and
a correlated double sampling (CDS) array suitable for generating an active sampling signal and a dummy sampling signal, which are sampled from the active pixel signal and the dummy pixel signal by using a correlated double sampling.

### Claim 25 (depends on 24)

The CMOS image sensor of claim 24, wherein the dummy pixel array includes an optical black (OB) pixel array.