Macromodeling of complex power delivery networks for efficient transient simulation

Simulation of power delivery networks has been traditionally done in the frequency domain, assuming a linear noise source represented by a Thevenin current source. As the technology progresses, power integrity needs to be maintained in spite of lower noise requirements with decreasing supply voltages below 1 V; and increasing current consumption. Hence more accurate simulation methodologies that take into account the non-linear behavior of ICs are becoming necessary. Transient simulation of a complex power delivery network in the presence of non-linear elements using SPICE is however computationally prohibitive. Hence, development of new efficient methodologies is critical for power integrity design in the time domain. In this paper, we use vector fitting to create a macromodel of a power delivery network by first calculating its frequency response. The generated macromodel is much smaller than the original power delivery network model, hence the efficiency is greatly improved. The macromodel needs to satisfy the property of passivity as in the original model. We present a new methodology to create guaranteed passive macromodels by construction.