Common Centroid Ambient Light Sensor Layout for Lower Parasitic Capacitance
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Solution Overview
Problem
Common centroid ambient light sensors are cumbersome and suffer from parasitic capacitances due to connections between photodiodes and readout circuits, which degrade noise performance.
Innovation Solution
A common centroid ambient light sensor design featuring a matrix of photodiodes with two rows and three color channels, where each color channel has a readout circuit connected to exactly one photodiode in each row, and all readout circuits are aligned perpendicular to the rows, reducing parasitic capacitance through daisy chain connections and shared analog-to-digital converters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If photodiodes are connected to readout circuits with multiple connections per color channel, then spatial variation sensitivity is reduced, but parasitic capacitance increases and noise performance degrades
Solution Approach 1:
The sensor is segmented into exactly two rows of photodiodes, with each color channel connecting to exactly one photodiode in each row. This segmentation reduces the number of connections compared to traditional multi-photodiode-per-channel designs, thereby reducing parasitic capacitance while maintaining common centroid geometry for spatial insensitivity
Solution Approach 2:
Each color channel is assigned a specific local connection pattern (one photodiode per row), creating localized readout paths. This local quality approach minimizes connection complexity and parasitic capacitance at each channel while preserving the overall common centroid arrangement
2Stability of the object's composition
If multiple photodiodes per color channel are used, then spatial variation sensitivity is reduced, but device complexity and connection parasitic capacitance increase
Solution Approach 1:
The photodiode array is segmented into exactly two rows, with each color channel connecting to precisely one photodiode in each row. This segmentation simplifies the connection topology compared to traditional designs with multiple photodiodes per channel, reducing device complexity while maintaining spatial insensitivity through the common centroid arrangement of the two rows
Solution Approach 2:
Instead of connecting multiple photodiodes to each color channel (traditional approach), the invention inverts the connection pattern by having each color channel connect to exactly one photodiode in each of the two rows. This inverted approach reduces connection complexity while achieving the same spatial insensitivity goal
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 design results in a less cumbersome sensor with reduced parasitic capacitance, improving noise performance and reducing the complexity of connections between photodiodes and readout circuits.
Implementation Method 1
each color channel comprise at least one photodiode configured to receive and detect light having wavelengths in a range corresponding to this color channel
Data Source
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AI summary
The present disclosure relates to a common centroid ambient light sensor (1) comprising: a matrix of photodiodes having exactly a first row (R1) and a second row (R2); at least three color channels (ChB, ChR, ChG) comprising a first color channel (ChR) and a second color channel (ChG); a readout circuit (RR) of the first color channel (ChR) connected to exactly one photodiode (PDR1) in the first row (R1) and exactly one photodiode (PDR2) in the second row (R2); and a readout circuit (RG) of the second color channel (ChG) connected to exactly one photodiode (PDG1) in the first row (R1) and exactly one photodiode (PDG2) in the second row (R2).