Image Sensor Driver Circuit for Low-Ripple Row Signal Transitions
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Solution Overview
Problem
Image sensing devices using CMOS technology face challenges in reducing row-wise temporal noise due to ripples in driving voltages during signal transitions, which affect the quality of captured images.
Innovation Solution
A driver circuit is designed with multiple voltage levels and units, including pull-up and pull-down driving units with different threshold voltages, and path coupling units to manage voltage transitions and reduce ripple in boosted and reduced voltage levels, thereby controlling current loads and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single driving voltage is used during signal transitions, then the circuit structure is simple, but row-wise temporal noise increases due to voltage ripples
Solution Approach 1:
The driving voltage generation is segmented into multiple units (first and second pull-up driving units, first and second pull-down driving units), each responsible for different voltage transition phases. This segmentation allows independent control of voltage ripples during different sections of signal transitions, reducing overall noise while maintaining manageable circuit complexity through modular design.
Solution Approach 2:
The circuit dynamically switches between different driving units based on the signal transition phase. During first section transitions, the first pull-up/pull-down units operate; during second section transitions, the second pull-up/pull-down units operate. This dynamic allocation optimizes noise reduction performance for each transition phase while maintaining circuit simplicity through selective activation.
2Object-affected harmful factors
If multiple voltage levels are used to reduce noise, then row-wise temporal noise decreases, but the device complexity increases
Solution Approach 1:
Different driving units provide different voltage levels (first high voltage, second high voltage, first low voltage, second low voltage) tailored to specific transition sections. Each unit is optimized for its specific function, creating local quality variations that reduce noise in critical areas while keeping the overall circuit structure manageable through specialized modular components.
Solution Approach 2:
The circuit changes voltage parameters (high voltage levels, low voltage levels, threshold voltages) across different operating sections to optimize noise reduction. By varying these electrical parameters according to signal transition phases, the circuit achieves superior noise performance without requiring a completely complex redesign, as parameter changes can be implemented through standard circuit design techniques.
Data Source
AI summary
A driver includes a first level shifting unit generating a second signal swinging in a second threshold range in response to a first signal swinging in a first threshold range, a second level shifting unit generating a third signal swinging in a third threshold range in response to the second signal, a first pull-up driving unit driving an output terminal with a first high-voltage in response to the second signal, a first pull-down driving unit driving the output terminal with a first low voltage in response to the third signal, a second pull-down driving unit driving the output terminal with a second low voltage higher than the first low voltage in response to the fourth signal, and a first path coupling unit coupling the second pull-down driving unit with the output terminal in response to the second signal.