----- Original Message ----- From: "Mark E. Skeels" To: "Microcontroller discussion list - Public." Sent: Wednesday, May 19, 2010 5:48 PM Subject: Re: [EE] Using a p-channel power mosfet for supply polarity > No, it would work, but it's the power dissipation. > > It will see ~ 40 Amps at times. It sits on a heat sink. > > A quick check on Digikey for a 45A, 60V schottky shows a drop of 600 mV. > > I'm pretty sure I can do better with a MOSFET, right? > > So the FET does not turn on, and conduction occurs only through the body > diode? So are you saying your application can not tolerate a drop of 600mV? If it can, I'd go with the schottky.. Your going to get some drop with the MOSFET - In the datasheet for your MOSFET, it has a ds resistance of 0.02 ohm at -10V gs, 38A. 38*0.02 = 760mV drop (I may be wrong, but it seems this way) -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist