IC Cell Replacement for Leakage Power Reduction
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Solution Overview
Problem
Integrated circuits (ICs) face challenges in reducing leakage power without compromising operational speed, as techniques to minimize leakage often increase delay, and existing methods for reducing leakage power are not effective in maintaining quality of results (QOR) metrics.
Innovation Solution
The approach involves using EDA tools to replace cell instances in IC designs with pivot variants that balance delay and leakage, breaking timing violations by converting positive slack to negative slack, and then recovering timing by swapping cells with lower delay but higher leakage variants, thereby optimizing power leakage while maintaining speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If threshold voltage is increased to reduce leakage power, then leakage power is reduced, but transistor delay increases
Solution Approach 1:
The patent applies local quality by selectively replacing cell instances with different variants based on their specific timing characteristics. Critical paths receive low-leakage variants with acceptable delay, while non-critical paths receive high-leakage variants with lower delay. This localized optimization resolves the contradiction by applying different leakage-reduction strategies to different parts of the circuit based on their timing requirements.
Solution Approach 2:
The patent changes the threshold voltage parameter selectively by choosing from multiple cell variants with different threshold voltage characteristics. The EDA tool analyzes timing slack and selectively applies high-threshold-voltage cells (low leakage, high delay) only where timing permits, while using low-threshold-voltage cells (high leakage, low delay) where timing is critical. This parameter-based differentiation resolves the contradiction between leakage reduction and delay maintenance.
2Loss of energy
If gate length is increased to reduce leakage power, then leakage power is reduced, but transistor delay increases
Solution Approach 1:
The patent applies local quality by selectively replacing cell instances with different variants based on their specific timing characteristics. Critical paths receive low-leakage variants with acceptable delay, while non-critical paths receive high-leakage variants with lower delay. This localized optimization resolves the contradiction by applying different leakage-reduction strategies to different parts of the circuit based on their timing requirements.
Solution Approach 2:
The patent changes the gate length parameter selectively by choosing from multiple cell variants with different gate length characteristics. The EDA tool analyzes timing slack and selectively applies long-gate-length cells (low leakage, high delay) only where timing permits, while using short-gate-length cells (high leakage, low delay) where timing is critical. This parameter-based differentiation resolves the contradiction between leakage reduction and delay maintenance.
3Loss of energy
If low leakage cell variants are used, then leakage power is reduced, but IC speed decreases
Solution Approach 1:
The patent applies local quality by selectively replacing cell instances with different variants based on their specific timing characteristics. Critical paths receive low-leakage variants with acceptable delay, while non-critical paths receive high-leakage variants with lower delay. This localized optimization resolves the contradiction by applying different leakage-reduction strategies to different parts of the circuit based on their timing requirements.
Solution Approach 2:
The patent applies partial action by selectively applying leakage-reduction measures only to non-critical paths where timing slack permits. Rather than uniformly optimizing all cells for low leakage (which would degrade overall IC speed), the tool applies low-leakage variants only where it provides benefit without harming timing, leaving critical paths with higher-leakage but faster variants. This partial optimization resolves the contradiction by avoiding excessive leakage reduction in speed-critical areas.
4Loss of energy
If conventional power optimization methods are used, then some leakage reduction is achieved, but quality of results metrics deteriorate
Solution Approach 1:
The patent applies feedback by using the EDA tool to iteratively analyze timing slack, identify replaceable cell instances, evaluate candidate variants, and update the design. The tool continuously monitors timing constraints and adjusts cell selections to maintain timing closure while reducing leakage. This feedback loop ensures that leakage reduction does not compromise timing requirements, thereby maintaining quality of results metrics while achieving power optimization.
Data Source
AI summary
A method for reducing leakage power of an IC during the design of the IC. A cell based IC design is received that includes a plurality of signal paths with positive slack. The positive slack is converted to negative slack by replacing cell instances in the IC design with footprint equivalent variants of the cell instances. The negative slack is converted back to positive slack via an iterative path-based analysis of the IC design. In each iteration, a path is selected that has negative slack and replacement values are computed for cell instances in the path. One or more cell instances in the path are then replaced with variants based on the replacement values.