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WEBENCH® Tools/LM25117: LM25117 high temperatures on high side FET

Part Number: LM25117
Other Parts Discussed in Thread: CSD18513Q5A

Tool/software: WEBENCH® Design Tools

I am working on a design using the LM25117.

The circuit seems to be working OK, my prototype boards are working and the regulator is able to produce the desired output.

However the high side FET gets extremely hot for some reason. After a few minutes of operation the solder melts, shorting out the FET and resulting in a burned PCB (I had multiple boards fail this way). The FET used is the CSD18513Q5A.

The rest of the board has pretty acceptable temperatures, including the low-side FET and the inductor.

What may be the cause for this failure? How can it be corrected?

  • Hi Fotis,

    Pls Simulate your circuit  with Webench and check the power loss of high-side FET, normally power loss round 2W or lower is acceptable.

    You can test board with much lower current, measure the high-side gate, SW node and inductor current waveforms to see what's the problem there.

    B R