Efficient switching window computation for cross-talk noise

In this paper, we present an efficient method for computing switching windows in the presence of delay noise. In static timing analysis, delay noise has traditionally been modeled using a simple switch-factor based noise model and the computation of switching windows is performed using an iterative algorithm where timing window propagation and switch factor updates are computed repeatedly until convergence. It was shown that the worst-case number of iterations required for convergence is O(n), where n is the number of gates in the circuit, resulting in an overall run time of O(n2). It was also shown that the iterations converge to different solutions, depending on the initial assumptions, making it unclear which solution is correct. In this paper, we show that the iterative nature of the problem is due to the switching-factor noise model and the order in which events are evaluated. Based on superposition model, we propose a time-sort based algorithm to compute the impact of delay noise on timing windows. We prove that the proposed algorithm has a run time that is linear with the circuit size. Since the algorithm is non-iterative and does not require initial assumptions, it eliminates the multiple solution problem. We tested the algorithm on a number of designs and show that it achieves significant speedup over the iterative approach.