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Diode required spec for TLV1117

Tiger Yeh
Expert 5675 points
Other Parts Discussed in Thread: TLV1117

Hi~

According to datasheet, an external diode is recommended for protecting TLV1117 if the input instantaneously is short to ground.

May I know what the minimum requirement for this diode? Is it okay to use 1N4148WS-F?

 

Thanks and Best regards,

Tiger

  • 0
    TI__Mastermind 24995 points

    Hello Tiger,

    The note and the diode chosen are for general guidance. 

    I can't say for sure that there is a minimum specification for the diode, just that it will depend on the application. 

    I am sure that you're aware that 1N4002 can handle more surge current than the 1N4148, so I would say that if the application doesn't exceed the specification of the 1N4148 when the input is shorted to ground, then using the 1N4148 should be acceptable.

    Best,
    Michael

  • 0 in reply to Michael J Schultis
    TI__Expert 3590 points
    Hi Michael,
    My customer has similar question need your advice, actually they are wondering why this external diode is needed? is it purpose to protect TLV1117 from surge current passing through internal ESD / parasitical diode? or thoer reason? please advise.
    Thanks,
    Martin
  • 0 in reply to Martin Chien
    TI__Mastermind 24995 points
    Martin,

    This diode isn't required, but is highly recommended if there is the potential for a short on the input.

    In brief, yes, this is necessary because of internal diode from OUT to IN, so there will be a large current flow to the input if there is an instantaneous short and this could permanently damage the device.

    There is also a good description of this in the applications section of the LP2985-33 datasheet.
    www.ti.com/.../lp2985-33.pdf

    Best,
    Michael