Imager Pixel Capacitance Circuit Boosting Reset Voltage
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Solution Overview
Problem
Conventional CMOS imagers require additional supply voltage boost circuits to achieve maximum voltage swing in the storage region, increasing size, power consumption, design complexity, and costs due to the need for external voltage boosting.
Innovation Solution
A capacitance circuit is used within the pixel circuit to boost the reset voltage of the floating diffusion region, eliminating the need for an external voltage source by employing one capacitor for increased storage capacity and another for boosting the reset voltage, thereby enhancing dynamic range without overboosting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If external voltage boost circuits are used to achieve maximum voltage swing in the storage region, then the dynamic range is improved, but the device size, power consumption, and design complexity increase
Solution Approach 1:
The patent extracts the voltage boosting function from external circuits and relocates it to an internal capacitor within the pixel circuit. Specifically, a second capacitor is coupled to the storage region to provide voltage boosting during reset operation, eliminating the need for external voltage boost circuits and their associated complexity
Solution Approach 2:
The patent makes the capacitor serve multiple functions: it acts as both a storage element for maintaining charge and as a voltage boosting element during reset. This multi-functionality eliminates the need for separate external voltage boost circuits, reducing overall device complexity while maintaining dynamic range performance
2Stability of the object's composition
If external voltage boost circuits are used to achieve maximum voltage swing in the storage region, then the dynamic range is improved, but the power consumption increases
Solution Approach 1:
The patent removes the power-consuming external voltage boost circuits by extracting the voltage boosting function and implementing it internally using a capacitor that can be charged from existing pixel circuit nodes, thereby reducing overall power consumption while maintaining dynamic range
Solution Approach 2:
The capacitor within the pixel circuit serves itself by being charged from the pixel's own internal nodes (such as the storage region or other charged nodes) and then discharging to provide the necessary voltage boost during reset, eliminating the need for external power sources and reducing power consumption
3Stability of the object's composition
If external voltage boost circuits are used to achieve maximum voltage swing in the storage region, then the dynamic range is improved, but the design complexity and costs increase
Solution Approach 1:
The patent extracts the voltage boosting functionality from complex external circuits and implements it using a simple capacitor that can be easily integrated into the pixel circuit during standard CMOS fabrication, thereby simplifying design and manufacturing while achieving the desired dynamic range
Solution Approach 2:
The patent achieves voltage boosting by changing the electrical parameters within the existing pixel circuit - specifically by utilizing capacitor charging and discharging cycles to temporarily increase voltage at the storage region during reset, rather than adding complex external voltage boost circuits
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 allows for increased dynamic range and signal output swing without the need for external voltage boosting, reducing power consumption and design complexity while maintaining high image quality.
Implementation Method 1
Capacitor 215 provides additional charge storage capacity
Implementation Method 2
another capacitor for boosting the reset voltage of the floating diffusion region
Data Source
AI summary
A pixel cell in which a capacitance is coupled between a storage node and a row select transistor and another capacitance is coupled between a storage node and a voltage supply or ground source potential to boost a reset voltage.