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June 2014 DocID025012 Rev 1 1/14
AN4337
Application note
The avalanche issue: comparing the impacts
of the I
AR
and E
AS
parameters
By Vittorio Giuffrida
Introduction
Generally, power MOSFETs are considered rugged with respect to the avalanche
phenomenon, however, the quantification of the level of ruggedness depends on the I
AR
avalanche current and
E
AS
avalanche energy. These two parameters determine the capacity
of a MOSFET to be safe during the avalanche. This paper explores the theory of the
avalanche effect in a flyback converter, in order to understand how the I
AR
and E
AS
parameters affect MOSFET operation and, consequently, how to manage a voltage
overshoot higher than the V
(BR)DSS
absolute maximum rating.
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