Improvements to the Analytical Model to Describe UIS Events

We generalize and refine an analytical model to describe unclamped inductive switching (UIS) events in power MOSFETs and derive a novel, fast method to extract thermal impedance and series resistance from the UIS waveform. We show excellent agreement between model and measurement for SiC MOSFETs. The method allows for the comparison of thermal impedance measurements of packaged parts to that of formerly not easily accessible waferlevel die. The model allows to evaluate UIS ruggedness and provides insight into the nature of ruggedness limitations. A figure of merit for UIS ruggedness is provided and different MOSFET architectures are compared with respect to UIS ruggedness.