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tps610981 VSUB turn on under load

Dan Hoshiko
Prodigy 110 points
Other Parts Discussed in Thread: TPS610981

I have a very light load of about 600 ohms or 2mA at 3V. I am wondering if I can use the mode pin as an enable line for my circuitry that is connected to the VSUB line.  The datasheet says that I need to be able to turn it on and off seperately from the mode pin.  Is this a hard requirement and if so, why?

  • 0
    TI__Intellectual 1305 points

    Hi Hoshiko,

    I don't quite understand your question.

    It is recommended in datasheet that turn on Vsub first and then enable the subsystem. It's also OK to enable Vsub and subsystem at the same time, because TPS610981 can statup with your 2mA load.

    Correct me if my understanding is wrong.

    BR,

    Gene

  • 0 in reply to Gene Lu
    Prodigy 110 points

    Just to clarify my question, I was wondering why the datasheet said to turn on Vsub first and then enable the subsystem.  It is states this because the TPS610981 can only start up with a very light load, I would want to know what that load is.  My circuitry does not have an enable so I would have to start the subsystem by enabling Vsub.

    It sounds like from what you said I can in fact use the MODE pin to enable Vsub and thus my subsystem at the same time since it is a very light load.

    That being said, how much of a load can be on VSUB for it to start up ok?

    Thanks,

    Dan

  • 0 in reply to Dan Hoshiko
    TI__Intellectual 1305 points

    Hi Dan,

    The statement in datasheet is just a recommendation for better performance, not a hard requirement. The current limit of LDO in TPS610981 200mA, and since you have alreadly turn the Vmain on before enable Vsub, 200mA startup can be supported.

    BR,

    Gene