Datasheet avalanche ratings

AN2344

14/27

Figure 9.

3.3.1

EAR (Energy during avalanche for repetitive pulse)

Often stated in the datasheet, this value is defined as the energy at IAR during repetitive

operation, and the value is usually calculated with a 10KHz power pulse train with a 50%

duty cycle and the nominal power rating of the device (see Equation 3).

Equation 3

should be equal to 15mJ. However, this value is redundant and not very useful for the

design, as it gives very poor information about the maximum energy to be dissipated and

into account the extra power dissipation introduced by the repetitive avalanche, and to

calculate the heat sink size required to dissipate it. Because of a triangular pulse:

Equation 4

And the additional average power to be dissipated is expressed as:

Equation 5

where,

f= Frequency (see Equation 3),

V= Peak voltage, and

I= Peak current

EAR=power/f

E

1

2

---VI

t

AV

•

=

P

AV

Ef

•

1

2

---VI

t

AV

•

f

•

=

=