Piecewise approximate circuit simulation

A simulation methodology for the nonlinear transient analysis of electrical circuits is described. Equations are formulated on the tree/link basis. All branch and node variables are modeling to be piecewise approximate in time. Electronic devices are represented by empirical table models of I-V characteristics. The table models may be built at various levels of precision, and concomitant accuracy levels are reflected in the simulation results. Simulation accuracy may be varied on a branch-by-branch basis or global basis, this permitting the user to distribute computer resources in a meaningful manner. The simulation algorithm is event driven and fully exploits temporal sparsity in the underlying circuit equations. Mechanisms for dealing with steady-state situations and stiff circuits have been investigated. A prototype simulator, SPECS, has been developed and tested on large industrial integrated circuits. It has proven to be a reliable and efficient tool in the analysis of digital and mixed circuits