Linear Equivalent Circuit and Current Source for I/O (LECCS-I/O) Modeling of IC Power Current for EMI Simulation

Abstract

In this paper, we describe how we modeled EMI noise from the power-pin current of an LSI that has two ports: a power-ground port and a driver output port. We called this the “Linear Equivalent Circuit and Current Source for I/O (LECCS-I/O) ” model, and have evaluated it using the measured power current and power-ground impedance of a small-scale IC (74LVC04) under various combinations of loading capacitances and decoupling inductances. Results showed that up to 500MHz, the LECCS-I/O model was able to predict peak and valley frequencies of the power current spectra within an error of 2.5MHz, and where the peak current error was less than 5dB. The application range of the LECCS-I/O model was valid where the shortest data duration was longer than twice the decay time constant of the power current under-damping waveform.