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LMZ10503: Failure

Ruben (TSR) Rivera
Prodigy 150 points
Part Number: LMZ10503

I am using some LMZ10503 regulators for 5V to 3.3V, 3.3V to 1.2V, and 3.3V to 1V conversions. We noticed in the lab that the outputs seemed to be tied to the input voltage rails. For example with the 5V to 3.3V conversion we were seeing 5V on the output. Similar with the 3.3V converters.

The datasheet routing guidelines mention having output resistors/capacitors on the same side of the board as the LMZ part, but ours are on the opposite side of the board. Would that cause this issue? We white-wired our feedback circuitry to the top of the part and that seemed to correct the issue. Any thoughts?

  • 0
    TI__Mastermind 21420 points

    Hi Ruben,

    There is a higher chance for noise to couple into the FB node when the FB resistors and capacitor are placed further away or on opposite side of the board. The routing can also add some inductance into the FB network and thereby change the compensation network.

    Best regards,

    Varun