Re: MOSFET body diodes

On Mon, 24 Oct 2005 17:42:26 GMT, "Mike Young"
<boat042-spam@xxxxxxxxx> wrote:

>I'm controlling a small DC motor with a MOSFET (irf7341). All diagrams I see
>have additional Schottky diodes in parallel with the MOSFET. I'm wondering
>if the body diode isn't enough in this application. The power level is
>small; I'm anticipating no more than 3A average drive current.
>
>You might have guessed my education here consists almost entirely of
>application notes and datasheets. Is it just the reverse recovery time that
>indicates the need for an additional diode? The irf7341 has a t-rr of 90ns
>max, which seems quite fast. What am I looking for to guide the design? What
>search terms can I use to Google more info?
>
>Thanks.
>Mike.

I have blown fets in h-bridges driving motors, at very low currents.
Seems the substrate diodes had a snap recovery characteristic that
blew the gates out somehow. These were older power fets, and I think
some newer parts are rated to survive this.

John

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