AN601

www.DataSheet.co.kr AN601 Vishay Siliconix Unclamped Inductive Switching Rugged MOSFETs For Rugged Environments The evolution of the power MOSFET has resulted in a very rugged transistor. The semiconductor industry defines this ruggedness as the capability to withstand avalanche currents when subjected to unclamped inductive switching. Historically, MOSFET manufacturers chose to quantify ruggedness, not based principally on individual performance, but rather on comparative performance with other manufacturers. Siliconix has optimized the cell structure of power MOSFETs, resulting in a new class of extremely rugged devices. Today’s avalanche-rated MOSPOWER FET exhibits a ruggedness that far exceeds the performance of any power MOSFET of earlier years. Symbols and Definitions Whenever possible, symbols and definitions established by the JEDEC Committee, JC-25, are used in this article. To clear up any discrepancies, however, the following list describes symbols used frequently in this article. IO L the peak current reached during avalanche tAV the time duration of the avalanche phenomenon the value of inductance the breakdown voltage in avalanche V(BR)eff What is Unclamped Inductive Switching? This application note reviews the history of unclamped inductive switching (UIS) and examines various theories pertaining to failure. It further identifies what appears to be two related mechanisms — thermal and bipolar — believed to be responsible for failure during unclamped induc...