In continuous regime now you have 30 Amp. X 0.0053 Ohm = 159 mW. It doesn't seem to be too much to heat the mosfet. But maybe you are switching the mosfet. You didn't tell anything about switching frequency. In that case the scenario is different. Cheers, Marcelo Fornaso ________________________________ From: Dwayne Reid To: pic microcontroller discussion list Sent: Mon, July 5, 2010 4:17:15 PM Subject: [EE] Looking for low RDSon N-ch Mosfet Good day to all. I'm looking at a buddy's project where his requirements have changed slightly. He's currently using a IRF1405 N-channel Mosfet with a data-sheet rating of RDSon = 5.3 Milli-Ohms. He's finding that the temperature rise is higher than he likes and is therefore looking for a Mosfet with lower RDSon. The circuit operates at less than 30 Vdc and he has at least 10V of gate drive available. He'd prefer to stay with the current TO-220 package if possible. Any suggestions? Recap: N-channel Mosfet, TO-220 package, Vds 30V max, Id 30A max, RDSon < 3 Milli-Ohms, > 10V gate drive available. Many thanks! dwayne -- Dwayne Reid Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax www.trinity-electronics.com Custom Electronics Design and Manufacturing -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist