From: Jim Thompson
Subject: Re: Selecting a heatsink?
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Date: Tue, 14 Jan 2003 21:06:58 GMT
NNTP-Posting-Date: Tue, 14 Jan 2003 16:06:58 EST
Organization: Cox Communications
On Tue, 14 Jan 2003 15:45:42 -0500,
Glenn Ashmore ,
In Newsgroup: sci.electronics.design,
Entitled: "Selecting a heatsink?",
Wrote the following:
|How do you properly size a heatsink for a MOSFET? What spec do you look
|at on the MOSFET data sheet to compare with the heatsink specs?
|For example: I want to run 6.5 amps through a MOSFET with a drain to
|source on resistance of .04 Ohms. I think the formula to get watts is
|I^2*R so I am generating about 1.7 watts. The thermal resistance is
|2.2ēC/W junction to case and .5ēC/W case to sink for a total of 2.7ēC/W
|times 1.7 watts is 4.7ēC above ambient. Am I correct so far? That
|sounds mighty low.
|Assuming I got that right, what do you look for in heatsinks using
There's the thermal resistance, heatsink-to-air, that you missed.
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| Jim-T@analog_innovations.com Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
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