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LMR33620-Q1: My buck is not regulating correctly.

Michael Nemshon
Prodigy 10 points
Part Number: LMR33620-Q1

When i had placed all components onto PCB I originally had a short but was quickly resolved. Now I am having the issue of no voltage regulation. My Vout closely matches mt Vin with minimal drop. Im expecting 3.3V. Only component not specifically mentioned in the datasheet is the 15uH. I also measured 3.5V at the FB pin, 5V at the Boot Pin. Any guidance as to what the issue might be would be very helpful.

 

  • 0
    TI__Expert 3835 points

    Hi Michael,

    If your output is tracking your input with minimal drop, I am guessing that you may have damaged the high side FET to always being on. 

    I have a couple of other questions below: 

    - Did the short have any possibility of damaging the device? Can you confirm the functionality of the device by swapping out with a different unit?

    - Can you share the layout?

    - What is the voltage at VCC?

    - Can you provide waveforms at SW?

    Regards,

    Ethan