Row Driver Circuitry for Imaging Devices with Boosted Voltage Management
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Solution Overview
Problem
Image sensors face reliability issues due to increased failure rates of transistors when operating at boosted voltages higher than the nominal operating voltage, which can lead to terminal voltage exceedance and reduced device reliability.
Innovation Solution
A row driver circuit design that includes an operating voltage supply and a boosted voltage supply, with a pre-driver generating a driver voltage at least the boosted amount above a reference voltage, and a series configuration of transistors to manage the output signal and keep terminal voltages within the operating voltage supply limits, preventing transistor failure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the voltage on pixel signals is boosted to improve performance and avoid fabrication differences, then the dynamic range and gating operation are improved, but the terminal voltages of transistors exceed the operating voltage supply causing reliability problems
Solution Approach 1:
The patent introduces an intermediary circuit structure between the boosted voltage supply and the transistor gates. This intermediary configuration allows the boosted voltage to be applied to the pixel array gates while preventing the boosted voltage from directly appearing across the transistor terminal, thus mediating between the performance benefit of boosted voltage and the reliability requirement of voltage containment.
Solution Approach 2:
The patent segments the voltage application path by separating the boosted voltage supply from the transistor terminal voltage path. Through this segmentation, the boosted voltage can be delivered to the pixel array for improved performance while the transistor terminals are kept at safe voltage levels through proper circuit configuration.
2Measurement precision
If boosted voltage is applied to reset and transfer gates to increase dynamic range, then the sensor dynamic range is improved, but the failure rate of transistors increases due to higher terminal voltages
Solution Approach 1:
The patent uses an intermediary circuit arrangement that allows boosted voltage to be applied to the reset and transfer gates for increasing dynamic range, while simultaneously preventing the boosted voltage from directly stress the transistor terminals, thus mediating between measurement precision improvement and reliability maintenance.
Solution Approach 2:
The patent changes the voltage parameters by applying boosted voltage only to specific gate terminals (reset and transfer gates) while maintaining different voltage levels at other critical points in the circuit. This selective parameter change allows dynamic range improvement without uniformly increasing all terminal voltages, thereby controlling the failure rate.
Data Source
AI summary
Row drivers as a part of an image sensor device include circuitry for supplying a plurality of signals with an increased voltage and enhanced reliability to a corresponding row in a pixel array. The row driver circuitry is designed to input a signal such as row select, reset or transfer and additionally input a boosted voltage supply. The row select, reset, or transfer signal is then output with a boosted voltage that is higher than the operating voltage supply. The row driver circuit is configured so that all terminal voltages across any of the plurality of transistors within the row driver circuit are less than or equal to the operating voltage supply.