SiPM Bias Current Precharge for Improved Subpixel Linearity

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Solution Overview

Problem

LIDAR systems using silicon photomultiplier (SiPM) devices face non-linearity issues due to parasitic capacitances that reduce the output current and cause high differential non-linearity, especially in detecting single photoelectron events and assessing the strength of return signals.

Innovation Solution

Implementing a current source using a bandgap connected to each subpixel current regulator to bias the microcell supply node, reducing the charge used to charge parasitic capacitances and improving linearity by precharging load capacitances with a precharge current regulator.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a silicon photomultiplier device is used to detect photons with high gain, then single photon detection capability is improved, but parasitic capacitances reduce output current and cause high differential non-linearity

Engineering Contradiction:

Improvesingle photon detection capabilityVSAvoidlinearity of subpixel characteristic response

Core Design Contradiction:

Measurement precisionVSManufacturing precision

Solution Approach 1:

The patent applies preliminary action by precharging the load capacitance before the SPAD detection event occurs. The current regulator precharges the capacitance associated with the microcell supply node and active devices, so that when a photon is detected and the SPAD conducts, the capacitance is already charged and does not steal charge from the output current, thereby maintaining linearity while preserving single photon detection capability

Inventive Principle:

Principle #10Preliminary action

2Measurement precision

If high gain is applied to photon detection, then detection sensitivity is improved, but charge is lost to charging parasitic capacitances reducing output current

Engineering Contradiction:

Improvedetection sensitivityVSAvoidoutput current

Core Design Contradiction:

Measurement precisionVSQuantity of substance

Solution Approach 1:

The current regulator performs preliminary charging of the parasitic capacitances before the SPAD avalanche event. By precharging the capacitance at the microcell supply node and the active device capacitances, the system ensures that when the SPAD detects a photon and generates output current, the capacitances are already charged and do not draw additional charge from the signal current, thus preserving both sensitivity and output current quantity

Inventive Principle:

Principle #10Preliminary action

3Device complexity

If conventional SiPM structure is used, then device simplicity is maintained, but differential non-linearity is high affecting signal assessment accuracy

Engineering Contradiction:

ImproveSiPM structure simplicityVSAvoidsignal assessment accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent introduces a current regulator as an intermediary component between the current source and the SPAD microcells. This regulator selectively precharges the parasitic capacitances associated with each microcell supply node, acting as a mediator that compensates for the non-linearity caused by capacitance charging without fundamentally redesigning the SiPM structure, thus maintaining simplicity while improving signal assessment accuracy

Inventive Principle:

Principle #24Intermediary (Mediator)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Enhances the linearity of subpixel characteristic response, ensuring a greater amount of charge is available for measurement, thereby improving the accuracy of single photoelectron event detection and return signal assessment.

Implementation Method 1

Avalanche detectors and silicon photomultipliers effectively apply high gain to the photon detection—in some cases a single photon may cause the avalanche breakdown within the detector, thereby creating a macroscopic output signal

Methodology Applied

Scientific EffectAvalanche breakdown: Avalanche Breakdown

Implementation Method 2

single photon avalanche detector (SPAD) configured to selectively conduct an output current in response to detecting a photon

Methodology Applied

Scientific EffectPhotoelectric effect: Photoelectric Effect

Implementation Method 3

The current source has a first load capacitance at the microcell supply node, and the at least one active device has a second load capacitance. The SiPM device also includes a current regulator configured to conduct a precharge current from the microcell supply node to precharge each of the first load capacitance and the second load capacitance

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentUS20250389819A1Silicon photomultiplier linearity improvement using bias current

Publication Date: 2025.12.25 SEMICON COMPONENTS IND LLC

AI summary

Silicon photomultiplier linearity using bias current. A silicon photomultiplier (SiPM) device includes: a single photon avalanche detector (SPAD) configured to selectively conduct an output current in response to detecting a photon; a current source defining a microcell supply node and configured to supply the output current to the microcell supply node; and at least one active device connected between the microcell supply node and the SPAD and configured to selectively conduct the output current therebetween. The current source has a first load capacitance at the microcell supply node, and the at least one active device has a second load capacitance. The SiPM device also includes a current regulator configured to conduct a precharge current from the microcell supply node to precharge each of the first load capacitance and the second load capacitance.