Industry White Paper

Understanding Power MOSFET Avalanche Operation and Associated UIS (UIL) Data Sheet Ratings

September 12, 2022 by onsemi
Topics Covered
  • Typical Ranges of Avalanche Voltages
  • UIS Data Collection
  • Power MOSFET Avalanche Operation

Application Note Overview 

The power function of a MOSFET operating in avalanche can be of any form. This application note covers a specific avalanche power function that forms the basis of avalanche ratings found on power MOSFET data sheets. MOSFET data sheets typically specify avalanche ratings under the synonymous terms "UIS" or "UIL" meaning "Unclamped Inductive Switch-off" or "Unclamped Inductive Load". That is, power MOSFET avalanche ratings apply to the resultant Vds and Is for p-channel MOSFET) waveforms when a MOSFET driving an unclamped load is switched off.