A simplified method of generating thermal models for power MOSFETs

There is an increasing need for designers to understand the thermal performance of the semiconductors they use because end-product case sizes are shrinking while product power levels remain the same or increase. A simulation tool such as P-SPICE is the most commonly available tool for engineers to use in performing thermal analysis of semiconductors. However, generating the thermal model for power semiconductors represents a major hurdle in performing such an analysis. A simplified method of model generation is needed. In this paper an Excel spreadsheet uses datasheet information published by the manufacturer to generate the R-C (resistance-capacitance) parameters for a thermal model. Implementation of the model in P-SPICE enables performance evaluation for any pre-defined operating condition. The intent is to arrive at a fair estimate of the junction temperature of the power-handling device, the MOSFET, under transient high-power pulse/s. The explanation of a proposed simplified method of thermal model generation includes an example featuring a power MOSFET.