Combining RC-interconnect effects with nonlinear MOS macromodels

This paper presents new techniques for accurately accounting for RC-interconnect effects in conjunction with nonlinear MOS macromodeling. RC-interconnects contribute to the delay of signals, but more importantly, they alter the shape of signals. Thus, circuit performance is affected by nonlinear transistors, secondary MOS effects, input waveform shape, and RC-interconnect loading. All these issues are addressed by the techniques presented here. An equivalent π-model for RC-interconnects is used in combination with advanced nonlinear MOS macromodeling to provide simulation results with accurate timing and, more critically, waveform shape of the gate output. Thus, the macromodel provides accurate simulation results whether the behavior is dominated by the nonlinear transistors or RC-interconnects. These techniques yield accurate circuit behavior at speeds two orders of magnitude faster than SPICE for even small circuits