# US 11,906,354 B2 · Recharge circuit for digital silicon photomultipliers

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- Number: US 11,906,354 B2
- Document ID: US11906354B2
- Status: Granted
- Kind: B2
- Application number: 17/626,464
- Filed: 2020-07-16
- Published: 2022-09-08
- Granted: 2024-02-20
- Earliest claimed: 2019-07-19
- Assignees: Avago Technologies International Sales Pte. Limited
- Applicants: Avago Technologies International Sales Pte. Limited
- Inventors: Thomas Frach; Torsten Solf
- Web page: https://patentgrep.com/patent/US11906354B2

## CPC

- G01J 1/44: Electric circuits {(for command of an exposure part G03B7/02)}
- G01T 1/248: {Silicon photomultipliers [SiPM], e.g. an avalanche photodiode [APD] array on a common Si substrate}
- A61B 6/037: {Emission tomography}
- G01J 2001/442: {Single-photon detection or photon counting}
- G01J 2001/4466: {Avalanche}
- 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)
- A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D)

## Abstract

The present application relates generally to silicon photomultiplier (SiPM) detector arrays. In one aspect, there is a system including an array of cells each including a single-photon avalanche diode (SPAD) reverse-biased above a breakdown voltage of the SPAD. Each cell may further include trigger logic connected to the SPAD, and configured to output a trigger signal indicating whether the SPAD is in breakdown. Each cell may still further include a conditional recharge circuit configured to recharge the SPAD conditional upon both (i) the recharge circuit applying the recharge signal to the cell and (ii) the trigger signal output by the trigger logic of the cell indicating the SPAD of the cell is in breakdown.

## Claims

### Claim 1

An optical detector, comprising:
an array of cells; and
a recharge circuit configured to apply a recharge signal to groups of cells of the array;
wherein each cell includes:
a single-photon avalanche diode (SPAD) reverse-biased above a breakdown voltage of the SPAD;
trigger logic connected to the SPAD, and configured to output a trigger signal indicating whether the SPAD is in breakdown; and
a conditional recharge circuit configured to recharge the SPAD conditional upon both (i) the recharge circuit applying the recharge signal to the cell and (ii) the trigger signal output by the trigger logic of the cell indicating the SPAD of the cell is in breakdown.

### Claim 2 (depends on 1)

The optical detector of claim 1 wherein:
the groups of cells of the array are rows of cells of the array; and
the recharge circuit for each row includes a recharge driver for outputting the recharge signal and an electrical conductor connecting the output of the recharge driver to the conditional recharge circuits of all cells of the row.

### Claim 3 (depends on 1)

The optical detector of claim 1 wherein the conditional recharge circuit is configured to recharge the SPAD by bringing the anode of the SPAD to electrical ground.

### Claim 4 (depends on 1)

The optical detector of claim 1 wherein:
the cells each further include a p-channel field-effect transistor (P-FET) (P1);
the recharge signal is connected to a gate of the P-FET (P1); and
the trigger signal is connected to a source of the first P-FET (P1).

### Claim 5 (depends on 1)

The optical detector of claim 1 wherein:
the recharge signal is connected to: a gate of a first p-channel field-effect transistor (P-FET) (P1), a gate of a second P-FET (P2), and a gate of a n-channel field-effect transistor (N-FET) (N1); and
the trigger signal is connected to a source of the P-FET (P1).

### Claim 6 (depends on 1)

The optical detector of claim 1 wherein the recharge signal comprises a pulse train with a duty cycle.

### Claim 7 (depends on 1)

The optical detector of claim 1 wherein the recharge signal has a variable pulse width.

### Claim 8 (depends on 6)

The optical detector of claim 6 wherein the recharge signal comprises 10 ns pulses.

### Claim 9 (depends on 6)

The optical detector of claim 6 wherein the duty cycle is 50%.

### Claim 10

A method comprising:
with trigger logic connected to a single-photon avalanche diode (SPAD), outputting a trigger signal indicating that the SPAD is in breakdown; and
with a conditional recharge circuit:
receiving the trigger signal indicating that the SPAD is in breakdown;
receiving a recharge signal indicating to recharge the SPAD;
in response to receiving the trigger signal indicating that the SPAD is in breakdown and receiving a recharge signal indicating to recharge the SPAD, recharging the SPAD.

### Claim 11 (depends on 10)

The method of claim 10 wherein the conditional recharge circuit recharges the SPAD by bringing the anode of the SPAD to a ground.

### Claim 12 (depends on 10)

The method of claim 10 wherein:
the recharge signal is sent to a gate of a P-FET (P1); and
the trigger signal is sent to a source of the P-FET (P1).

### Claim 13 (depends on 10)

The method of claim 10 wherein:
the recharge signal is sent to: a gate of a first p-channel field-effect transistor (P-FET) (P1), a gate of a second P-FET (P2), and a gate of a n-channel field-effect transistor (N-FET) (N1); and
the trigger signal is sent to a source of the first P-FET (P1).

### Claim 14 (depends on 10)

The method of claim 10 wherein the recharge signal comprises a pulse train with a duty cycle.

### Claim 15 (depends on 14)

The method of claim 14 wherein the recharge signal comprises 10 ns pulses.

### Claim 16 (depends on 15)

The method of claim 15 wherein the duty cycle is 50%.

### Claim 17

An optical detector, comprising:
an array of cells each including:
a single-photon avalanche diode (SPAD) reverse-biased above a breakdown voltage of the SPAD; and
trigger logic connected to an anode of the SPAD, and configured to output a trigger signal;
wherein each cell of the array is configured to connect the SPAD to a ground when a recharge signal is applied, and wherein the recharge signal comprises a pulse train with a duty cycle.

### Claim 18 (depends on 17)

The optical detector of claim 17 wherein the recharge signal comprises 10 ns pulses.

### Claim 19 (depends on 17)

The optical detector of claim 17 wherein the duty cycle is 50%.

### Claim 20 (depends on 17)

The optical detector of claim 17 wherein at least one of the duty cycle and a cycle length of the pulse train is configurable.