Common Centroid Ambient Light Sensor Layout for Lower Noise Readout

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Solution Overview

Problem

Common centroid ambient light sensors suffer from being cumbersome and having parasitic capacitances due to connections between photodiodes and readout circuits, which degrade noise performance.

Innovation Solution

A common centroid ambient light sensor design with a matrix of photodiodes arranged in two rows, where each color channel has a readout circuit connected to exactly one photodiode in each row, and shared analog-to-digital converters reduce parasitic capacitances by minimizing connections and optimizing layout.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If connections between photodiodes and readout circuits are made in known common centroid ambient light sensors, then the sensor can detect light in multiple color channels, but parasitic capacitances are introduced that degrade noise performance

Engineering Contradiction:

Improvemulti-color channel detection capabilityVSAvoidparasitic capacitances degrading noise performance

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

Multiple color channels share common readout circuits and analog-to-digital converters, reducing the total number of connections and parasitic capacitances while maintaining multi-color detection capability

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

Readout circuits and ADCs are designed to serve multiple color channels universally, allowing a single circuit to process signals from different photodiodes corresponding to different color channels

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If multiple readout circuits are provided for each color channel in known common centroid ambient light sensors, then each photodiode can be independently read out, but the device becomes cumbersome and complex

Engineering Contradiction:

Improveindependent readout capabilityVSAvoidcumbersome structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Readout circuits and ADCs are shared across multiple color channels, consolidating what would otherwise be separate independent readout paths into unified circuits that serve multiple functions

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

Each readout circuit and ADC is designed to handle signals from multiple photodiodes across different color channels, eliminating the need for dedicated circuits for each channel while maintaining readout independence

Inventive Principle:

Principle #6Universality (Multi-functionality)

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

The sensor is less cumbersome and exhibits reduced parasitic capacitances, improving noise performance and efficiency by shortening connections and sharing readout circuits.

Implementation Method 1

each color channel comprises at least one photodiode configured to receive and detect light having wavelengths in a range corresponding to this color channel

Methodology Applied

Scientific EffectPhotoelectric effect: Photoelectric Effect

Data Source

PatentUS12474203B2Ambient light sensor having common centroid layout

Publication Date: 2025.11.18 STMICROELECTRONICS (RES & DEV) LTD

AI summary

A common centroid ambient light sensor includes a matrix of photodiodes having exactly a first row and a second row, at least three color channels, a readout circuit of the first color channel connected to exactly one photodiode in the first row and exactly one photodiode in the second row, and a readout circuit of the second color channel connected to exactly one photodiode in the first row and exactly one photodiode in the second row.