Si Power Device|Evaluation

Mechanisms of MOSFET Destruction -Summary-


Up to this point, we have discussed SOA destruction, avalanche breakdown-induced destruction, and dV/dt destruction of MOSFETs. Of course, the absolute maximum ratings in the specifications for a MOSFET must not be exceeded, but in addition, choosing circuit designs and operation conditions based on an understanding of the mechanisms of these destruction types is extremely important for the safe use of MOSFETs.

Below are links to the articles and the key points of each.

About SOA (Safe Operating Area)Destruction

Key Points of This Article

・SOA is an abbreviation of Safe Operating Area, meaning the range within which operation is safe.

・MOSFETs and other devices are used within the SOA range.

・There are five conditions that set limits on the SOA; if any of these are exceeded, destruction is possible.

About Destruction due to Avalanche Breakdown

Key Points of This Article

・When a voltage equal to or greater than the absolute maximum rating BVDSS is applied to a MOSFET, avalanche breakdown occurs.

・When avalanche breakdown occurs, a large current flows, and there is the risk of MOSFET destruction.

・MOSFET destruction due to avalanche breakdown may be short-circuit destruction or thermal destruction.

About dV/dt Destruction

Key Points of This Article

・dV/dt destruction is a phenomenon in which the charging current flowing through the parasitic capacitance Cds while a MOSFET is turned off flows through the base resistor RB, causing the parasitic bipolar transistor to switch to the on state and leading to short-circuit destruction.

・dV/dt is the voltage change per unit time; the steeper the rise of VDS, the more readily dV/dt destruction occurs.

・In general, the poorer the reverse recovery characteristic, the steeper dV/dt becomes, and the greater the tendency for destruction.

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