Leakage Mitigation Circuit for Imaging Pixel Storage Nodes
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Solution Overview
Problem
Storage nodes in imaging pixels are susceptible to leakage, especially under high ambient temperature, long signal integration time, or manufacturing processes creating devices with smaller off-resistances, leading to incorrect outputs, and existing positive feedback circuits are prone to noise coupling and transient current disruptions.
Innovation Solution
A leakage mitigation circuit with a single transistor and self-biased device, forming a positive feedback loop that inverts signals to maintain original levels without external timing control, using minimal components and unaffected by temperature or manufacturing variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional positive feedback circuits with two inverters are used for leakage mitigation, then leakage can be reduced, but the circuit complexity increases and susceptibility to noise coupling occurs
Solution Approach 1:
The patent extracts only the essential feedback function needed for leakage mitigation, implementing it with a single transistor rather than the conventional two-inverter structure. This removes unnecessary circuit elements while retaining the core leakage mitigation capability, thereby reducing device complexity without sacrificing reliability.
Solution Approach 2:
The patent implements a simplified feedback mechanism using a single transistor that provides the necessary positive feedback for leakage mitigation. This feedback loop continuously monitors and corrects leakage currents, maintaining signal integrity at the storage node while using minimal circuitry, thus resolving the contradiction between reliability and device complexity.
2Reliability
If conventional positive feedback circuits are used for leakage mitigation, then leakage can be reduced, but susceptibility to transient current disruptions increases
Solution Approach 1:
The patent implements a circuit design that is inherently more resistant to transient current disruptions from the outset. The single-transistor feedback configuration and self-biased device create a more stable operating point that naturally cushions against transient disturbances, preventing them from triggering false feedback activation while maintaining effective leakage mitigation.
3Area of stationary object
If storage capacitance is reduced to minimize device size, then device area decreases, but leakage susceptibility increases
Solution Approach 1:
The patent implements a self-biased device that automatically adjusts its operating point based on the actual leakage conditions at the storage node. This self-service mechanism continuously compensates for leakage currents without requiring external control, enabling the circuit to maintain reliability even with reduced storage capacitance and minimal device area.
Solution Approach 2:
The patent utilizes parameter changes in the self-biased device to dynamically adapt to varying leakage conditions. By adjusting the biasing parameters based on real-time operating conditions, the circuit maintains optimal leakage mitigation performance regardless of storage capacitance size, thereby resolving the contradiction between device area and leakage susceptibility.
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
Effectively mitigates leakage in imaging pixels by maintaining signal integrity across varying conditions, reducing susceptibility to transient currents and noise, and eliminating the need for large capacitors or timing controls.
Implementation Method 1
The inverter inverts the signal to a second voltage level. A single transistor coupled to the inverter and the storage node inverts the signal output by the inverter to the first level to hold the signal at the storage node to its original level.
Implementation Method 2
A self-biased device coupled to the inverter lowers current disturbance related to the storage node. The self-biased device can limit a maximum current that can flow through the inverter.
Implementation Method 3
The inverter and the single transistor can form a positive feedback circuit. The voltage level of the signal at the storage node can be unaffected by a leakage path connected to the storage node.
Data Source
AI summary
A leakage mitigation circuit is provided. The leakage mitigation circuit includes an inverter coupled to a storage node, wherein the storage node receives a signal output by an imaging pixel having a first voltage level to be stored. The inverter inverts the signal to a second voltage level. A single transistor coupled to the inverter and the storage node inverts the signal output by the inverter to the first level to hold the signal at the storage node to its original level. A self-biased device coupled to the inverter lowers current disturbance related to the storage node and increase threshold voltage at which fluctuation of the level of the signal at the storage node causes the signal to be inverted by the inverter.