Power Current Model of Digital IC With Internal Impedance for Power Decoupling Simulation

One of the main sources of radiated emission from a digital PCB is high-speed switching current flowing on power supply pins of IC/LSI. To suppress the emission, the power decoupling technique is effective. To estimate and to reduce the EMI, we need a behavior model to simulate high frequency current at power supply pins of an IC. In this paper, the authors propose an equivalent circuit model that is composed of an equivalent internal current source and an equivalent internal impedance to express power current penetrating an IC from a power pin to the ground. To verify the model, simulated results of reduction of high frequency current when inserting a series inductor on a power supply line is shown with correspondent results of measurement.