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Old 04-26-2014, 09:26 PM
Khenglish Khenglish is offline
Join Date: Mar 2012
Posts: 28

I put the fets in the clevo. High side fets are failing after 1-3 minutes of light use. The source and drain are shorting. Ocp is saving the mobo and cpu, but obviously this is very bad. They are failing 1 at a time. The 2nd fet in the phase does not die when the other does. They are not even warm when they die. No discoloration, just source and drain shorted together for apparently no reason. Both failures so far have been in the same phase.

Could I just have a bad batch of parts or did I do something wrong?

Answered my own question. It was bad fets. It was the new fet that died. I pulled it without adding a new one and I've been running prime95 for a while now.

The question now is should I try to put the 2nd high-side fet in for phase 2. I could pull the one I put in the older dell since I know it works, but I am so incredibly sick of this. The FET swap did fix my power limit issues. I now no longer have throttling over 75W. I feel like there has to be some benefit though of having the 2nd FET in, or else the pad wouldn't even be there and much weaker FETs would be used for the high-side to minimize switching losses.

Update 2:

I tried the high-side FET I put in the dell. It worked fine at the desktop (the last 2 died shortly after loading the desktop), but died 2 minutes into prime95 at 4.4ghz. Again the existing FET in phase 2 was unharmed. Unless someone has something insightful very soon, I'm just putting it back together with only 1 high-side fet in the 2nd phase. I still have 2 untested FETs, but I'd rather not bank the CPU and mobo's health on OCP kicking in a 4th time.

Last edited by Khenglish; 04-27-2014 at 02:43 PM.
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Old 06-01-2014, 11:34 PM
Khenglish Khenglish is offline
Join Date: Mar 2012
Posts: 28

Well I had even more high-side FETs fail, and the last one killed the CPU VRM (now outputs an invalid PWM signal for IGP voltage, despite never touching IGP circuit). Mouser had the VRM in stock. Hopefully I can replace it properly.

Does anyone have a suggestion for high-side FETs from someone other than TI? Unfortunately the CSD17507Q5A that I attempted to use for high-side FETs seems to have far better specs than anything else (which is why I picked it). Is there a manufacturer that has similarly specced 5x6mm FETs that I am missing?
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