AN2344

Testing avalanche ruggedness

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Testing avalanche ruggedness

The avalanche capability of the device is usually evaluated by using a circuit that performs

an Unclamped Inductive Switching (UIS) operation like the one shown in Figure 2. The

operation is as follows:

1.

At zero time, the device switches ON, closing the circuit.

2.

The current increases following an exponential law as a function of the L/R

characteristics of the circuit, which are caused by the presence of an inductance, given

3.

As soon as the device is switched OFF, the dI/dt causes an overvoltage on the drain of

the device because the magnetic field in the inductance cannot instantaneously go to

zero (see Figure 3.).

Figure 2.

UIS reference diagram

Figure 3.

Typical UIS waveforms