# US 2018/0323229 A1 · Readout architecture for event-driven pixels

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- Number: US 2018/0323229 A1
- Document ID: US20180323229A1
- Status: Published application
- Kind: A1
- Application number: 15/588,576
- Filed: 2017-05-05
- Published: 2018-11-08
- Earliest claimed: 2017-05-05
- Assignees: Kiskeya Microsystems LLC
- Inventors: Babak Nouri
- Web page: https://patentgrep.com/patent/US20180323229A1

## CPC

- H10F 39/803: {Pixels having integrated switching, control, storage or amplification elements}
- G01J 1/4228: {arrangements with two or more detectors, e.g. for sensitivity compensation}
- G01J 1/46: using a capacitor
- G01T 1/17: Circuit arrangements not adapted to a particular type of detector {(pulse-selection circuits H03K, G01R)}
- H04N 25/47: Image sensors with pixel address output; Event-driven image sensors; Selection of pixels to be read out based on image data
- H10F 39/18: Complementary metal-oxide-semiconductor [CMOS] image sensors; Photodiode array image sensors
- H10F 77/95: {Circuit arrangements}
- G01J 2001/4473: {Phototransistor}
- H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
- G01J: MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY (light sources F21, H01J, H01K, H05B; investigating properties of materials by optical means G01N)
- G01T: MEASUREMENT OF NUCLEAR OR X-RADIATION (radiation analysis of materials, mass spectrometry G01N23/00; tubes for determining the presence, intensity, density or energy of radiation or particles H01J47/00)
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION

## Abstract

Methods and systems for reading out a pixel array are provided. An example system may include a plurality of pixels. The system may further include an interface circuit configured to provide an analog signal at a sense node. The analog signal may represent the activity of at least two pixels. The interface circuit may include a plurality of capacitors of which at least one capacitor is connected at one end to an output stage of a pixel and at another end to the sense node. The system may further include a readout circuit configured to convert the analog signal at the sense node to a digital signal.

## Claims

### Claim 1

A device, comprising:
a plurality of pixels;
an interface circuit configured to provide an analog signal at a sense node, the analog signal being representative of the activity of at least two pixels, the interface circuit including a plurality of capacitors of which at least one capacitor is connected at one end to an output stage of a pixel and at another end to the sense node;
a readout circuit configured to convert the analog signal at the sense node to a digital signal.

### Claim 2 (depends on 1)

The device according to claim 1, further comprising a transistor having a terminal connected to the sense node.

### Claim 3 (depends on 1)

The device according to claim 1, wherein the one capacitor is a metal-oxide-semiconductor (MOS) capacitor.

### Claim 4 (depends on 2)

The device according to claim 2, wherein the transistor is configured to provide a high resistance path from the sense node to a node held at a predetermined potential.

### Claim 5 (depends on 1)

The device according to claim 1, wherein the digital signal is a binary word.

### Claim 6 (depends on 5)

The device according to claim 5, further comprising a counter configured to output the binary word.

### Claim 7 (depends on 5)

The device according to claim 5, wherein the readout circuit is configured (i) to generate an adaptive reference using a pulse train based on the analog signal (ii) count the pulse train to generate the binary word.

### Claim 8

A method, for use with a device comprising a plurality of pixels, the method comprising:
representing activity of least two pixels as at least two digital signals; and
dynamically aggregating the at least two digital signals into one representative analog signal corresponding to an activity of the at least two pixels.

### Claim 9 (depends on 8)

The method according to claim 8, further comprising converting the dynamically aggregated signal into a representative digital word corresponding to the activity of the at least two pixels.

### Claim 10 (depends on 8)

The method of claim 8, wherein the dynamically aggregated signal is indicative of a number of events occurring simultaneously in the at least two pixels.

### Claim 11 (depends on 8)

The method of claim 8, wherein the at least two pixels are each a single photon avalanche diode (SPAD).