Circuit Timing Analysis Using Cell-Specific Derate Values
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Solution Overview
Problem
Traditional timing analysis methods for integrated circuits rely on universal derate values, which can lead to inaccurate predictions of path characteristics and pessimistic worst-case performance due to the assumption that all gates in a circuit are at the same parameter corner, resulting in overstatement or understatement of delays and potential manufacturing violations.
Innovation Solution
Determining derate values specific to each cell in a circuit based on its context, including path depth, output load, and input slew rate, to improve the accuracy of timing analysis and reduce variation, thereby aiding in optimizing circuit design and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If universal derate values are used for all gates in the circuit, then the timing analysis can be performed quickly and simply, but the accuracy of path characteristics prediction deteriorates and pessimistic worst-case performance occurs
Solution Approach 1:
The patent applies local quality by determining derate values specific to each cell based on its local context (path depth, output load, input slew rate) rather than using universal derate values for all gates. This allows each cell to have customized timing characteristics that reflect its actual operating conditions, improving prediction accuracy while maintaining computational efficiency through selective customization.
Solution Approach 2:
The patent segments the circuit into individual cells and evaluates each cell's contribution to timing variation separately. By breaking down the overall timing analysis into cell-level contributions and combining them statistically, the method achieves both computational efficiency and improved accuracy compared to universal derate approaches.
2Device complexity
If universal derate values are used for all gates in the circuit, then the analysis process remains simple, but manufacturing precision deteriorates due to overstatement or understatement of delays
Solution Approach 1:
The patent determines derate values specific to each cell based on its local context including path depth, output load, and input slew rate. This localized approach captures the actual timing behavior of each cell in its specific operating context, improving manufacturing precision by reducing both overstatement and understatement of delays while maintaining reasonable analysis complexity.
3Productivity
If all gates are assumed to be at the same parameter corner, then the analysis is computationally efficient, but reliability deteriorates due to inaccurate timing violation detection
Solution Approach 1:
The patent segments the timing analysis into individual cell evaluations, where each cell's derate value is determined based on its specific context. By combining these segmented cell-level analyses statistically, the method achieves both computational efficiency and improved reliability in timing violation detection compared to assuming all gates are at the same parameter corner.
Solution Approach 2:
The patent changes the parameter approach by determining derate values based on actual circuit operating conditions (path depth, load, slew rate) rather than assuming a fixed parameter corner for all gates. This dynamic parameter adjustment improves reliability of timing violation detection while maintaining computational efficiency through systematic evaluation.
Data Source
AI summary
A method for timing analysis of a circuit design includes, for each group of one or more instances of a cell of a cell library in the circuit design, determining timing related data for the group according to circuit context of the group in the design. The context includes at least one of a path depth, an output load, and an input slew rate. The determined timing related data are applied to analyze the circuit design.