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LM25088MH-1 WEBENCH Troubleshooting

Sebastian Fernandez
Prodigy 10 points

Hi!
I'm trying to run a 3.3V/7A power supply with LM25088MH-1.
As a beginner in power supply design, I tried to keep it simple and use a WEBENCH report as a reference design (Here).

I have changed some parts:
- MOSFET (M1): BSZ097N04LS
- Inductor (L1): SRP1250-4R7M
- Schottky (D1): MBRB1545CTG
- Output cap (Cout): EEE-FP1V331AP

My pcb design is almost the same as the LM25088MH-1's reference design.
When the PSU is turned on with no load, the output voltage is higher than it should be (almost 7V), and when I connect the load voltage decreases. If I connect 1ohm load, the output voltage is 0.5V.

Could someone tell me what should I check or what measurements can I make to solve this problem? I'll use a 100Mhz oscilloscope.

Thank you very much for your help!

  • 0
    TI__Guru 59001 points

    Hi Sebastian

    This should work. I think there is a simple mistake we don't know. Please check these items;

    -Cold Solder Joint

    -Ccomp and Chf are swapped each other.

    -SRP1250-R47M is misplaced for SRP1250-4R7M.

    -Rsns is not 10mohm or it is higher than 10m Ohm with some reason.

    If everything is right, please check VCC voltage whether it is in regulation.

    If VCC is right in regulation, please capture SW node waveforms at no-load and full-load for me.

    Regards,

    Eric