Half-Cycle Timing Pessimism Removal in IC Design Tools
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Solution Overview
Problem
Conventional design tools for integrated circuits are overly pessimistic in timing analysis for half-cycle clock paths, leading to excessive path slack penalties due to inability to apply common path pessimism reduction methods across rising-edge-to-falling-edge or falling-edge-to-rising-edge paths.
Innovation Solution
An automated design tool that identifies common circuit elements in half-cycle timing paths, determines PVT scaling values, calculates a total PVT compensation value, and generates a corrected timing report by subtracting this value from the total skew, effectively reducing pessimism in timing analysis for half-cycle paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional CPPR methods are used for rising-edge-to-rising-edge or falling-edge-to-falling-edge paths, then pessimism is reduced, but half-cycle paths (rising-edge-to-falling-edge or vice versa) do not receive CPPR benefits and remain overly pessimistic
Solution Approach 1:
The patent extends the CPPR method to work universally across all clock path types including half-cycle paths. By identifying common circuit elements in source and destination clock paths and calculating PVT compensation values, the method achieves pessimism reduction for rising-edge-to-falling-edge and falling-edge-to-rising-edge paths, making the CPPR technique applicable to all clocking schemes rather than being restricted to same-edge transitions.
2Reliability
If exhaustive searches of all possible PVT parameter combinations are used, then worst-case path delays are identified, but the analysis becomes computationally intensive
Solution Approach 1:
The patent extracts and removes the PVT variation component from common circuit elements in half-cycle paths. By identifying common elements between source and destination clock paths and calculating their PVT compensation values, the method separates the common-mode PVT variations from the differential timing analysis, thereby reducing computational complexity while maintaining worst-case coverage.
3Reliability
If bounding methods are used assuming slowest conditions for late delays and fastest conditions for early delays, then worst-case coverage is provided, but the results are overly pessimistic
Solution Approach 1:
The patent changes the parameter treatment by introducing PVT compensation values that adjust the bounding method results. Instead of uniformly applying worst-case PVT assumptions, the method calculates specific PVT compensation values for common circuit elements and applies them to correct the timing analysis, thereby reducing pessimism while maintaining reliability.
Data Source
AI summary
A design tool for reducing half-cycle common path pessimism includes program instructions storable on a computer readable medium. The program instructions may be executable by a processor to receive a timing report for the IC. For each source clock path and destination clock path of each half-cycle timing path, the design tool may identify common circuit elements, and determine a process, voltage, and temperature (PVT) path delay value corresponding to PVT scaling of each identified common circuit element. The design tool may sum together the PVT path delay values of each identified common circuit element to obtain a total PVT compensation value. The design tool may also generate a new total skew value by subtracting the total PVT compensation value from a total compensated skew value, and generate a corrected timing report that includes the new total skew values.