Differential Circuit Switching to Limit CMOS Aging Mismatch
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Solution Overview
Problem
Aging effects in deep nanometer complementary metal-oxide semiconductor (CMOS) processes cause mismatch buildup in integrated circuits, leading to performance degradation and reliability issues, as devices experience asymmetric aging conditions resulting in directional offset buildup, which traditional compensation techniques may fail to address effectively.
Innovation Solution
Implementing chopper stabilization using butterfly switches to reverse and limit the directional offset buildup by flipping the orientation of inputs and outputs of differential circuits, and systematically controlling the connections to arrays of differential circuits to equalize or reverse stress conditions across them.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If deep nanometer CMOS processes are used to make circuits more compact and faster, then circuit performance and integration density are improved, but aging effects cause mismatch buildup and reliability degradation
Solution Approach 1:
The patent applies periodic stress reversal by systematically flipping the orientation of inputs and outputs of differential circuits at regular intervals. This periodic action causes the aging-induced offset to reverse direction, preventing unbounded mismatch buildup while maintaining the high-performance benefits of deep nanometer CMOS processes.
2Measurement precision
If asymmetric stress conditions are applied to differential circuits, then directional offset buildup occurs, but this can be systematically reversed by flipping input-output orientation
Solution Approach 1:
The patent exploits the asymmetric nature of aging-induced offset by deliberately applying asymmetric stress conditions and then systematically reversing them. By flipping the input-output orientation of differential circuits, the method converts the harmful asymmetric offset buildup into a reversible effect, improving offset control accuracy.
Solution Approach 2:
The core mechanism involves inverting the orientation of inputs and outputs of differential circuits at regular intervals. This inversion reverses the direction of aging-induced offset, allowing the system to counteract mismatch buildup. The control circuit systematically applies these inversions to maintain precision while managing the complexity of connection control.
3Reliability
If traditional compensation techniques are used to address aging, then some offset correction is achieved, but they fail to effectively bound directional offset buildup
Solution Approach 1:
Instead of using complex continuous compensation mechanisms, the patent employs simple periodic flipping of differential circuit orientations. This periodic action effectively bounds the directional offset buildup by reversing it at regular intervals, achieving reliable offset control with minimal added complexity compared to traditional compensation techniques.
Data Source
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AI summary
Aging effects on devices fabricated using deep nanometer complementary metal-oxide semiconductor (CMOS) processes can cause circuits to exhibit an undesirable mismatch buildup over time. To address the aging effects, the connections to an array of M differential circuits are controlled to limit and systematically minimize or reverse the aging effects. In one embodiment, the controlling permutation sequence is selected to stress the array of M differential circuits under opposite stress conditions during at least two different time periods. Imposing opposite stress conditions, preferably substantially equal opposite stress conditions, can reverse the direction of a mismatch buildup and limit the mismatch buildup over time within acceptable limits. The controlling permutation sequence can be applied to an array of comparators of an analog-to-digital converter, or an array of differential amplifiers of a folding analog-to-digital converter.