Clock Tree Skew Mitigation via Critical Pair Segmentation
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Solution Overview
Problem
Existing circuit design processes struggle to efficiently mitigate local skew without negatively affecting the power, performance, and area (PPA) of the circuit, often relying on suboptimal heuristic methods due to the large number of local skew pairs.
Innovation Solution
The proposed method involves determining data path slack values and clock arrival values for a circuit's clock tree, calculating a total local skew value, and updating the clock tree to adjust timings, thereby mitigating skew while maintaining circuit performance and reducing processing resources and time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If traditional heuristic methods are used to mitigate local skew, then the number of skew pairs can be reduced, but the processing time and computational resources increase significantly
Solution Approach 1:
The patent segments the clock tree into multiple regions and identifies only the critical skew pairs within each region, rather than analyzing all possible pairs globally. This segmentation approach reduces the computational complexity from O(n²) to O(k) where k is the number of critical pairs, significantly reducing processing time while maintaining skew mitigation effectiveness.
Solution Approach 2:
The patent extracts and identifies only the critical skew pairs that have the most significant impact on circuit performance, rather than treating all skew pairs equally. By extracting the most important skew relationships and focusing mitigation efforts on those specific pairs, the processing time is reduced while maintaining effectiveness.
2Reliability
If skew mitigation techniques are applied to improve circuit performance, then timing violations are reduced, but the power, performance, and area (PPA) may be negatively affected
Solution Approach 1:
The patent applies skew mitigation selectively to specific local regions and critical skew pairs rather than uniformly across the entire circuit. By adjusting clock arrival times only where necessary to fix timing violations, the patent avoids unnecessary PPA penalties while maintaining timing reliability in critical paths.
Solution Approach 2:
The patent applies partial skew mitigation by focusing only on the most critical skew pairs that cause timing violations, rather than attempting to optimize all skew relationships. This partial action approach achieves sufficient timing reliability without the excessive computational overhead and PPA penalties that would result from comprehensive optimization.
3Measurement precision
If comprehensive skew analysis is performed on all clock pairs, then accurate skew values are obtained, but the computational complexity and processing resources increase
Solution Approach 1:
The patent segments the clock distribution network into regions and performs skew analysis only on critical pairs within each region. This segmentation maintains measurement precision for critical paths while reducing computational complexity from analyzing all possible pairs to analyzing only the most significant subset.
Solution Approach 2:
The patent performs partial skew analysis by focusing computational resources on identifying and measuring only the critical skew pairs that impact timing closure, rather than comprehensively analyzing all clock pairs. This approach achieves sufficient measurement precision for design closure with reduced computational complexity.
Data Source
AI summary
A system and method updates a clock tree based on skew values of the circuit design. The clock tree is updated by obtaining a circuit design that includes circuit elements and a clock tree. The clock tree includes clock sources and clock sinks. Data path slack values for the clock tree are determined based on the clock sources and the clock sinks. Further, clock arrival values for the clock tree are determined based on the clock sources and the clock sinks. A first total local skew value of the circuit design is determined based on the data path slack values, and the clock arrival values, and updating the clock tree based on the first total local skew value.