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TPS23861EVM-612: 3v3 current rating of lm5007 design

howard banks
Intellectual 580 points
Part Number: TPS23861EVM-612
Other Parts Discussed in Thread: LM5007, TPS23861, LM5017

I'm putting together a PoE injector board using the TS23861 and have seen the eval board.

I was wondering whether somebody could tell me what the expected max output current of the LM5007 switcher circuit on the eval board is.

I'm looking to supply 4x TPS23861 and one set of USB optos. I estimate that i need no more than 60mA on my 3v3 supply and was going to use the LM5007 as is. I just need to know what its capable of supplying.

Thanks.

  • 0
    TI__Intellectual 1695 points
    Hi Howard,

    TPS23861 VDD current consumption will be 6mA max, so I think that 60mA should work and it is OK to use LM5007 which can supply up to 500mA.
    The EVM of LM5007 is 10V/400mA output.
    Thank you.

    Best Regards
    Jack Chen
  • 0
    TI__Intellectual 1695 points
    Hi Howard,

    One more thing you need to pay attention to is that the power on sequence of VDD(3.3V).
    The VDD should be rise to its UVLO after the VPWR(48V) has risen up to UVLO(18.5V) because the reset pin should be pulled to low before the VPWR rises up to UVLO and it is usually connected to VDD(3.3V).

    So it is recommended to use a converter which has adjustable UVLO to control the power on timing of 3.3V like LM5017.

    Thank you