Incremental Timing Analysis for Coupled Noise in IC Design
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Solution Overview
Problem
Conventional static timing analysis in VLSI design fails to accurately account for capacitive coupling effects, leading to inefficiencies in incremental timing analysis and prolonged design optimization due to the need for full design re-analysis, which is cumbersome and inaccurate.
Innovation Solution
A method for incrementally calculating the impact of coupling noise on timing using previously computed sensitivities of delay and slew with respect to changes in coupling capacitance, limiting analysis to the downstream cone of logic from the change, and applying delay and slew adjusts to the timing analysis engine.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional static timing analysis is performed with coupling effects, then timing accuracy is improved, but computational complexity and analysis time increase significantly
Solution Approach 1:
The patent segments the design into victim paths and aggressor paths, allowing separate analysis of coupling effects. By dividing the timing analysis into independent path segments and using switching windows to identify relevant interactions, the computational complexity is reduced while maintaining timing accuracy for coupled nets.
Solution Approach 2:
The patent performs preliminary calculation of switching windows and K-factors before the main timing analysis. By pre-computing the switching windows for victim and aggressor nets and determining K-factors in advance, the actual timing analysis can proceed more efficiently without recalculating these parameters during the main analysis pass.
2Productivity
If incremental timing analysis is performed without coupling effects, then analysis speed is improved, but timing accuracy deteriorates
Solution Approach 1:
The patent pre-calculates switching windows and K-factors for coupling effects before incremental timing analysis. This preliminary computation allows the incremental analysis to quickly update timing by applying pre-determined coupling adjustments rather than recalculating coupling effects from scratch, maintaining both speed and accuracy.
Solution Approach 2:
The patent introduces switching windows as an intermediary mechanism that mediates between incremental timing changes and coupling effects. The switching windows act as a filter to determine which coupling interactions are relevant for each incremental change, allowing fast incremental updates while maintaining accurate coupling consideration only where necessary.
3Measurement precision
If full design re-analysis is performed for each design change, then timing accuracy is maintained, but design optimization time increases
Solution Approach 1:
The patent segments the design into affected and unaffected portions based on the location of design changes. By identifying only the victim paths and aggressor paths that are actually impacted by a design change and analyzing only those segments, the patent avoids redundant re-analysis of the entire design while maintaining timing accuracy for the affected portions.
Solution Approach 2:
The patent pre-computes switching windows and coupling K-factors that remain valid across multiple design iterations. These preliminary computations are reused for incremental updates, allowing rapid evaluation of design changes without repeating the full coupling analysis, thus reducing design optimization time while maintaining accuracy.
4Measurement precision
If coupling effects are included in incremental timing analysis, then timing accuracy is improved, but computational overhead increases
Solution Approach 1:
The patent uses switching windows as an intermediary to efficiently manage coupling effect calculations in incremental analysis. The switching windows pre-identify relevant time intervals and path interactions, allowing the incremental analysis to quickly determine which coupling effects need to be recalculated and which can be reused from previous analyses, reducing computational overhead.
Solution Approach 2:
The patent performs preliminary computation of switching windows and K-factors that can be reused across incremental analysis steps. By pre-establishing these coupling parameters before incremental updates, the patent avoids redundant calculations during each incremental step, reducing computational overhead while maintaining accurate coupling effect inclusion.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach improves the accuracy and speed of optimization tools by efficiently updating timing information, reducing runtime and enabling more precise detection of timing issues during signoff analysis.
Implementation Method 1
Coupling capacitance occurs when two neighboring wires are in close proximity of each other. Depending on how the signals rise or fall on these wires, delay and slew change on the victim net
Data Source
AI summary
A method for incrementally calculating the impact of coupling noise on the timing of an integrated circuit (IC) having a plurality of logic stages by performing an initial timing analysis on the IC to provide a first determination of the impact of coupling noise on the timing. One or more design changes to the IC are then performed. In response to the design change, the impact of the coupling noise to the timing is calculated on the logic stage where the change was made and on the logic stages downstream thereof. The results of the calculations are then inputted to a timing analysis tool to adjust the delay and slew of each logic stage where the design change was made and to the logic stages downstream thereof.