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From: email@example.com (Bob Wilson)
Subject: Re: Question about linear derating factor for MOSFETs
Date: Mon, 11 Nov 2002 04:38:23 -0000
Organization: Your Organization
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References: <firstname.lastname@example.org> <email@example.com>
In article <firstname.lastname@example.org>,
>>>> ** No, the case temp will need to be measured. It will have a
>>>>significant thermal loss depending on mounting arrangement and the
>>>>temp of the heatsink immediately under the device pack is the one that
>Ahh...of course, makes sense now. Seems like I could derive the case
>temp knowing the load, the heat sink temp (under load), the calculated
>junction temp, and the thermal resistances of the device (theta-jc)
>and the thermal grease?
>Otherwise, the heat sinks I'm considering have a hole drilled to
>directly underneath the center of the mounting location for the
>MOSFET. I can use that for a thermistor. Actual temperature
>measurement, for me, is the best way to verify performance for this
>situation. But I'd prefer to get a decent idea of the temperatures
>beforehand though...those bonded-fin heat sinks (Melcor) are very
>>>> ** I suspect it is going to be difficult to safely achieve 350 watts
>>>>dissipation from one device unless liquid cooling is used.
>I agree. I forgot to mention that this example was only to see if I
>understood the math. I'm limiting the load to 125-150 watts.
Still far to high unless you do something to reduce the thermal resistance
of your case to heatsink interface. See my earlier post.
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