[SOLVED] pulsed drain current question?

[babatundeawe]

Can someone please shed more light on pulsed drain current and continous drain current of power mosfets.

thanks
abm

 

[FvM]

The terms are self-explanatory to some extent, I think.

The datasheet numbers usually refer to more detailed specifications, particularly SOA (safe operating area) and transient thermal impedance.

A clearer question would be helpful.

 

[babatundeawe]

ok, this is where i am confused about the two.

when will i need to use pulse drain current of a mosfet and when will i need to use the continuous drain current.

for example, should i consider the pulsed drain current when i am using pulses(signal) e.g pwm signal to drive the mosfet and when i am usng the mosfet as a switch then i can consider the continuous drain current.

thanks

 

[FvM]

It's good design practice not to exceed the continuous ratings in normal operation. You possibly need to apply derating to power and current numbers according to available heatsinks in your design.

 

[dick_freebird]

If you meet continuous conditions, then you're golden
and everything else is design margin in pocket.

You would think that pulsed limits would look like
continuous limit / duty cycle. But at some point this
will fall away from that line as other reliability effects
take over. The pulsed rating, and especially the use
conditions they rate it at, which should be specified
are informative. However what happens when you
deviate from those conditions, may not be so clear.

Designing to continuous limits will leave $ or performance
on the table. But it's often what you have to do, to be
reliable in the face of unknown future abuse.

 

[babatundeawe]

thanks guys i got your message