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LP2981: suplying voltage regulator with 3,3V on output pin

Martin Mueller90
Prodigy 10 points
Part Number: LP2981

I have a LP2981-33DBVR to generate 3,3V out of 12V of a switching power supply.

For programming the board the PCB only can be supplied with 3,3V (12V not possible). So 3,3V is connected directly to the output pin of the LP2981-33DBVR, without voltage on the input pin. There is no external diode between output and input of the LP2981-33DBVR. Might this be a problem for the LP2981-33DBVR (pre-damage the device)?

Should I add an external diode between output and input to have voltage on the input pin?

  • 0
    TI__Guru 55940 points

    Hi Martin,

    When Vout exceeds Vin there is the intentional for reverse current to flow.  While there is a parasitic diode from OUT to IN, this diode is not characterized and the current through it is not limited.  We recommend that if Vout is expected to exceed Vin, that a Schottky diode be placed in parallel to this internal parasitic diode from OUT to IN.  This Schottky diode will provide a robust path for the reverse current.

    Very Respectfully,

    Ryan