Simulation of a coupled signal and power delivery system in an electronics package

As system operating frequencies and signal edge rates continue to increase, signal corruption in the form of crosstalk and noise in power delivery systems are becoming more and more limiting factors in the performance of electronic packaging. A variety of schemes have been devised to model package power delivery systems and signal trace coupling. In this paper, we present a novel approach to model such systems in a combined manner. The IO power delivery system is modeled in detail by discretizing all planes and vias and considering appropriate bypass capacitors on the chip and on the package. A simple two-port circuit model is then created that accurately reproduces the frequency and time domain responses of the detailed power delivery system model. Coupled signal lines are modeled using a culprit-victim methodology that accounts for many line coupling in a simplified four-port circuit for single-ended signals or an eight-port circuit for differential pairs. These two models are then combined to create a relatively simple SPICE model that simultaneously captures the effects of signal line behavior (e.g., crosstalk, reflections) with IO power delivery system behavior (e.g., rail collapse). This combined model provides a convenient vehicle to investigate the impact of a variety of packaging design variables on system IO performance. The development and use of such a combined model is demonstrated.