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LP2986 and Schottky protection

Other Parts Discussed in Thread: LP2986

I have some difficulties to choose a Schottky diode to protect my LP2986.

Vin is a battery between 0V and 14.7V, I have two LP2986, one @ 3.3V and a another @ 5V.

What are the criteria for choosing my diode?
Thanks you
  • No criteria really. A general purpose Si diode could probably work as well, but the Schottky was specified to give a bit more headroom.

    BAT54, or similar, is a good choice.

    If both LP2986 inputs go to common connection at battery (i.e. in parallel), then BAT54-C could be used.

    If the LP2986 are in series ( Vbatt > LP2986-5.0 > LP2986-3.3 >) then a diode across each device is required and BAT54-S could be used.

     

  • OK thanks you for the reference.

    My LP2986 are in parallel.

    So, I apply the schematic in datasheet, but i do not understand the operation :
    When Vin <Vout (abnormal operation), the diode is blocking? And when to Vin> Vout?

  • When Vin < Vout (abnormal operation) the external Schottky diode is conducting (ON) and the reverse current flows through the external Schottky diode, and not through the parallel internal parasitic diode/SCR.

    When Vin > Vout (normal operation) the external Schottky diode is blocking (OFF).

  • Thank you for this clarification.