Imager Pixel Architecture with Enhanced Column Discharge
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Solution Overview
Problem
Conventional semiconductor imaging devices require significant circuitry, limiting the size reduction and pixel fill factor, as they need dedicated reset control lines and associated drivers, which occupy space and hinder miniaturization.
Innovation Solution
The reset transistor is controlled by a signal on the column line, eliminating dedicated reset control lines and reducing circuitry, allowing for internal reset operations and enhanced column discharge using an NMOS transistor for faster readout.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dedicated reset control lines and drivers are used, then reset operation reliability is improved, but device complexity and area increase
Solution Approach 1:
The column line is made to serve dual purposes: it functions as both the signal readout line and the reset control line. By making the column line universal, the patent eliminates the need for separate dedicated reset control lines and their associated drivers, thereby reducing circuit complexity while maintaining reset operation reliability through the shared column line infrastructure.
2Manufacturing precision
If dedicated reset control lines are used, then reset control precision is improved, but area occupied by circuitry increases
Solution Approach 1:
The patent merges the reset control function with the existing column line infrastructure. By combining the reset control line with the column readout line, the design consolidates multiple functions into a single physical line, thereby reducing the total area occupied by circuitry while maintaining precise reset control through proper timing and voltage management on the shared line.
3Device complexity
If conventional column discharge is used, then circuit simplicity is maintained, but readout speed decreases
Solution Approach 1:
The patent introduces dynamic control of the column line voltage to enhance discharge speed. By actively managing the voltage transitions on the column line during readout operations, the system achieves faster signal readout speeds without significantly increasing circuit complexity, as the enhancement is achieved through operational dynamics rather than additional static circuitry.
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 reduces the size and complexity of imaging devices, enabling larger photodiode areas and potentially faster readout times by eliminating dedicated reset lines and using enhanced column discharge for quicker signal processing.
Implementation Method 1
The photodiode 162 converts incident photons to electrons which are selectively passed to a floating diffusion stage node A through transfer transistor 190 when activated by the TX control signal.
Data Source
AI summary
A pixel circuit includes a photosensor and a floating diffusion node. A circuit is coupled to the floating diffusion node, for selectively providing a pixel output signal to a column line. A reset circuit, which resets the floating diffusion node, is configured to be activated by the column line. A pullup circuit is included for controlling the reset circuit through a signal on the column line. A discharge circuit, which is separate from the reset circuit, is used for discharging the pixel output signal on the column line. The discharge circuit includes a transistor having a first source/drain terminal coupled to the column line and a second source/drain terminal coupled to a fixed voltage level. The gate of the transistor activates the discharging of the column line.