POSTSCRIPT: This got even more wandering "chain of consciousness" than sometimes. I lack time to edit well and just slashing stuff out MAY lose a few gems. So here 'tis as is - MAY start OK and get better again towards the end. Or not. Summary: More cowbell - or more Vgs MAY help Note 25C ratings Note "pulse" ratings. Note delta Rdson with temperature curves. Nice MOSFET ________________ At one stage most people who wrote power transistor spec sheets used to be tobacco company lawyers and ad men in a previous incarnation, or were moonlighting. A lot of those have gone, but they taught a few lessons which are occasionally at least partially remembered by some sometimes. As a rule of thumb, doubling the front page typical Rdson gives a figure which is safe in most cases. Some companies have got much better with this than heretofore and give figures for Tj=3D rather hot and DC steady state. Others give "pulse" spes = at say 25C. Some say what "pulse" means in their case. Some don't. Generally "pulse" means so brief that the die hardly changes temperature and with a low enough duty cycle that it cools essentially completely before the next pulse. This is not totally dishonest as long as you understand what they are doing and allow for it. They don't always make it clear. If you think Tj may end up at about 100C say you can use eg fig 8.6 in the data sheet http://www.semicon.toshiba.co.jp/info/docget.jsp?type=3Ddatasheet&lang=3Den= &pid=3DTK100E06N1 to scale Rdson wrt ambient. Peering at fig 8.6 I'd say a multiplier of 1.4 for Rdson_100C/Rdson_25C should be high. High is a good idea. You say you are using about 9V gate drive. That's OK - more is always useful (as long as not gate oxide death too much more :-) ) Fig 8.1 and 8.2 seem to be identically labelled but I suspect one is intended to be at 25C and the other at 125C At 10V gate drive work out the Rdson at a convenient point - Say about 82A/0.2V and 184 A/0.4V on figs 8.1 and 8.2 Or about 2.4 and 2.2 mOhm. Sounds good. That's fully driven - your about 9V should be 'about' as good. 10A @ 2.4 mR =3D 0.24W x Tja of 83C/W =3D~ 20C rise. Say Ta =3D 25C so Tj =3D 45C. Rdson multiplier 45c/25c ~~~~=3D 1.2 So delta T =3D 25C so Tj =3D 50C Iterate ... The increases get smaller. Lets try an 88C Tj as it crosses the 2.5 milliOhm line there. That's up from 1.85?? milliOhm ON THAT GRAPH at 25C for a multiplier of 2.5/1.85 =3D 1.35. Hmm that's about the 1.4 I guestimated to start. Will it get that high by this recursive process? You'd think not. BUT this just gives the multiplier with temperature - actual Rdson as above is different. You seem to be seeing say 95C (95-25) =3D 70 C rise 70 C / 83 C/W =3D 0.84 Watt At 10A Rdson =3D (P / I^2) =3D 0.84/100 =3D 8.4 milliOhm T100C/T25C Rdson mult ~~~=3D 2.65/1.85 =3D 1.43:1 So T25 pulse Rdson =3D 8.4/1.43 =3D 5.9 milliOhm That's more like what you'd expect from around Vgs of 5.5V. Measure your "about 9V) at rge FET Actual =3D ? What happens when you make Vgs "about 12V"? Russell On 23 December 2014 at 17:51, Jesse Lackey wrote: > Hi all, I have a project where I'm putting up to 10 amps through a NFET > connected to ground as per typical. Things are working fine except I'm > seeing a much larger temperature rise in the FET than expected. > > The FET is Toshiba TK100E06N1,S1X > Datasheet: > < > http://www.semicon.toshiba.co.jp/info/docget.jsp?type=3Ddatasheet&lang=3D= en&pid=3DTK100E06N1 > > > @ digikey: > < > http://www.digikey.com/product-search/en?x=3D0&y=3D0&lang=3Den&site=3Dus&= keywords=3DTK100E06N1S1X-ND > > > > The specs say 2.3 mOhm @ 50amps@10V (from digikey info) and 1.9 mOhms > typical from the datasheet. I'm driving it with a gate driver running > at approx 9V. > ... > > > --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .