SILCA: SPICE-accurate iterative linear-centric analysis for efficient time-domain Simulation of VLSI circuits with strong parasitic couplings

Abstract

A new circuit analysis method, named SPICE-accurate iterative linear-centric analysis (SILCA), is proposed for the efficient and accurate time-domain simulation of deep submicron very large scale integrated (VLSI) circuits with strong parasitic couplings. SILCA consists of two key linear-centric techniques applied to time-domain nonlinear circuit simulation. For numerical integration, explicit-formula substitution and iterative-formula transformation are presented to convert implicit variable time-step integration to fixed leading coefficient (FLC) variable time-step integration. This paper characterizes both convergence and stability properties of the resulting FLC integration formulae. For nonlinear iteration, a successive variable chord (SVC) method is used as an alternative to the Newton-Raphson method. Further, the low-rank update technique is implemented for fast LU factorization. With these techniques, the number and cost of required LU factorizations are reduced dramatically. Experimental results on nonlinear circuits coupled with substrate and power/ground networks have demonstrated that SILCA achieves more than an order of magnitude speedup over SPICE3 in terms of both the cost of LU factorization and the overall CPU time. SILCA is suitable for efficient SPICE-like time-domain simulation of parasitic-coupled VLSI circuits, where the number of linear parasitic elements dominates the number of nonlinear devices