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LM3480: Doesn't work up to maximum rated input voltage

Erich Zelmer
Prodigy 10 points
Part Number: LM3480

The LM3480IM3-3.3/NOPB voltage regulator will not work in our test circuit with Vin above 16V.  When Vin > 16V the output voltage begins to decrease to ~ 2.6V and current is limited to < 30mA.  Ambient temperature was around 30C.  The chip was mounted on an adapter with a small thermal plane.  The load current at 3.3V is 41mA.  Should this voltage regulator work in this application?

  • 0
    TI__Expert 3655 points

    Hello Erich,

    It sounds like you have 520mW+ of dissipation when attempting to source 41mA. That would equate to a temperature rise of 140C (520mW x 269.6C/W) or greater depending how far above 16V you're operating. I suspect the LDO is going into thermal shutdown since the junction could be estimated to be 170C (140C + 30C) or greater. 

    ~ Aaron