Victim Alignment in Crosstalk-Aware Timing Analysis

Modeling the effect of coupling-noise on circuit delay is a key issue in static timing analysis and involves the victim-aggressor alignment problem. As delay-noise strongly depends on the skew between the victim-aggressor driver input transitions, it is not possible a priori identify the victim-driver input transition that results in the worst-case delay-noise. Several approaches have been proposed in literature which heuristically search for the worst-case victim-aggressor alignment. This paper presents an analytical result that obviates the need to search for the optimal victim-driver input transition, thereby simplifying the victim-aggressor alignment problem significantly. Using the properties of standard nonlinear complementary metal-oxide semiconductor drivers, it is shown that for monotonic input transitions the worst-case victim-driver input transition is the one that switches at the latest point in its timing window. Similarly, the victim-driver input alignment at the earliest point in the timing window is optimal for early-mode analysis. Although this result has been empirically observed in the industry, to the best of our knowledge this is the first paper which provides a rigorous analysis and shows that the above result holds for both linear and nonlinear drivers. It is also shown that the latest alignment of the victim-driver input transition results in the latest victim receiver output arrival time even for the cases where the victim is coupled to multiple aggressors. Finally, experimental results show that limiting the alignment of the victim to only the latest victim-driver input transition can significantly reduce the runtime of existing approaches with no loss of accuracy.