AN601
Key Features
- thermal and bipolar
- believed to be responsible for failure during unclamped inductive switching and concludes by remending how a power MOSFET should be qualified for ruggedness in the data sheet. Whenever current through an inductance is quickly turned off, the magnetic field induces a counter electromagnetic force (EMF) that can build up surprisingly high potentials across the switch. Mechanical switches often have spark-suppression circuits to reduce these harmful effects that result when current is suddenly interrupted. However, when transistors are used as the switches, the full buildup of this induced potential may far exceed the rated breakdown (V(BR)DSS) of the transistor, thus resulting in catastrophic failure. If we know the size of the inductor, the amount of current being switched, and the speed of the switch, the expected potential may be easily calculated as V where L di/dt VDD = = = the inductance (H) rate of change of current (A/s) the supply voltage (V) = L di/dt + VDD (1)
