Pixel Internal Reset Control via Column Line Signal
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Solution Overview
Problem
Conventional semiconductor imaging devices require significant circuitry, which limits their size reduction and pixel fill factor, necessitating a reduction in circuitry to minimize imager size and enhance photodiode area.
Innovation Solution
The reset transistor is controlled by the signal on the column line, eliminating dedicated reset control lines and associated circuitry, allowing for a more compact pixel design and shared floating diffusion nodes among photodiodes, thereby reducing the area needed for the imager.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional reset control circuitry is used with dedicated reset control lines for each pixel, then reliable reset operation is achieved, but pixel area and imager size increase
Solution Approach 1:
The patent merges the reset control function into the column line signal path by coupling the reset control line to the column line at the output of the pull-up circuit. This allows the column line to serve dual purposes: signal readout and reset control, eliminating dedicated reset control lines and reducing pixel area while maintaining reliable reset operation through the shared control path.
Solution Approach 2:
The column line is given multi-functionality by using it both for signal readout and for controlling the reset transistor. The column line signal serves as both the data transmission medium and the reset control signal, allowing one circuit element to perform multiple functions and thereby reducing the overall circuit complexity and area.
2Manufacturing precision
If more circuitry is included in each pixel for independent reset control, then reset precision is improved, but device complexity increases
Solution Approach 1:
The patent extracts the reset control function from the individual pixel circuit and relocates it to the column line level. By removing the dedicated reset control lines and their associated control logic from each pixel, the pixel circuit complexity is reduced while the reset precision is maintained through the shared column line control mechanism that operates on all pixels in a column simultaneously.
Solution Approach 2:
The column line automatically serves the dual function of signal transmission and reset control without requiring additional control circuitry. The pull-up circuit at the column line output inherently provides the reset control signal to the reset transistor, allowing the system to self-regulate the reset operation without external dedicated control lines.
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
This approach decreases the size of the image sensor and corresponding circuitry while maintaining operational efficiency, allowing for a larger photodiode area and improved pixel fill factor.
Implementation Method 1
The photodiode 162 converts incident photons to electrons which are selectively passed to a floating diffusion stage node A
Data Source
AI summary
A pixel having no dedicated reset control line. By using the voltage on the column line to control the gate of the reset transistor, there is no need to provide a dedicate reset control line.