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Topic: How come my MOSFET was a "smoking", I thought it was rated high enough. (Read 5 times) previous topic - next topic

Grumpy_Mike

#20
Sep 25, 2012, 06:51 am Last Edit: Sep 25, 2012, 12:56 pm by Grumpy_Mike Reason: 1
No that FET needs 10V to turn it on. The gate threshold is where it just starts to turn on not when it is on fully. Look for the voltage the quote when they quote the on resistance.

By the way if you switch a 50W load the switch does not dissipate 50W, only the on current flowing through the on resistance.

dc42

Formal verification of safety-critical software, software development, and electronic design and prototyping. See http://www.eschertech.com. Please do not ask for unpaid help via PM, use the forum.

apples

yeah I agree I have been chasing my tail looking up numbers and I too think they are limited in what they sell.


apples

dc42, wow great link, and I can now browse them all via the rds(on) voltage.  cool.



dc42

One thing to watch for is that Rds(on) is often quoted at less than the maximum rated drain current. Always look at the datasheet and check that Rds(on) is quoted at or above the maximum drain current that you want to switch, for Vgs = 5V or lower.

btw I should have checked the 4V and 4.5V boxed for Rds(on) test voltage as well as the 5V box.

Many mosfets have Rds(on) quoted at both 10V and at 5V or 4.5V, and in these cases the Element14 site often indexes them under 10V. So there are probably many other suitable mosfets available at Element14.

If you definitely won't need a heatsink, then you can consider power mosfets in packages other than TO220, for example IPAK. One of my favourites is http://au.element14.com/international-rectifier/irlu8726pbf/mosfet-n-ch-30v-86a-ipak/dp/1698317 (Rds(on) = 8 milliohms max @ 4.5V 20A).
Formal verification of safety-critical software, software development, and electronic design and prototyping. See http://www.eschertech.com. Please do not ask for unpaid help via PM, use the forum.

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