Variable Voltage Row Driver for CMOS Image Sensor Noise Reduction
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Solution Overview
Problem
Conventional CMOS image sensors face challenges with limited chip area for drive signal transfer and performance degradation due to the use of fixed voltage sources, which introduces unwanted noise as pixel sizes shrink and control methods become more complex.
Innovation Solution
A Variable Voltage Row Driver is introduced to provide adjustable driving voltages to transistors in CMOS image sensors, using a control logic circuit to generate signals that adjust the magnitude of driving voltages on row lines, allowing for more precise control of transistor operations and reducing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed voltage source is used to drive transistors in pixels, then the circuit design is simple, but noise is introduced and performance degrades as pixel sizes shrink
Solution Approach 1:
The patent applies the Dynamics principle by transitioning from fixed voltage sources to variable voltage sources that can dynamically adjust their output voltage levels. The row driver circuit responds to control signals to provide different voltage magnitudes to row lines, enabling adaptive control of transistor operations. This dynamic approach allows the system to optimize performance for different operating conditions while maintaining reliability as pixel sizes shrink.
Solution Approach 2:
The patent implements Parameter changes by modifying the voltage parameter from a fixed value to a variable value that can be adjusted based on operational requirements. The row driver circuit changes the voltage magnitude on row lines in response to control signals, allowing optimization of transistor switching characteristics and reduction of noise effects. This parameter adjustment capability resolves the contradiction by enabling performance optimization without significantly increasing overall system complexity.
2Measurement precision
If pixel sizes are reduced to increase resolution, then higher resolution is achieved, but chip area for drive signal transfer becomes more limited
Solution Approach 1:
The patent applies the Universality principle by designing a row driver circuit that can serve multiple functions: driving different rows of pixels, providing different voltage levels for different operational modes, and controlling multiple transistor operations (transfer, reset, readout). This multi-functional approach allows the limited chip area to be used more efficiently, as the same row driver infrastructure supports various pixel operations without requiring separate dedicated circuits for each function.
3Adaptability or versatility
If control methods become more complex to manage transistor operations, then better performance control is achieved, but the chip area for transferring different drive signals is reduced
Solution Approach 1:
The patent implements Segmentation by dividing the control function into distinct segments: control logic circuits that generate control signals and row driver circuits that execute the driving functions. This segmentation allows complex control methods to be implemented through coordinated simple components rather than requiring a monolithic complex circuit. The control signals are segmented into different types (transfer, reset, readout) that can be managed independently, optimizing chip area usage while maintaining versatile transistor control capability.
Data Source
AI summary
An example image sensor includes a plurality of pixels arranged in an array of columns and rows, a row driver, and a control logic circuit. The row driver is coupled to pixels in a row of the array to provide a variable driving voltage to drive transistors included in the pixels of the row. The control logic circuit is coupled to provide one or more control logic signals to the row driver. The row driver adjusts a magnitude of the driving voltage in response to the one or more control logic signals.