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Original question:

tps27081 load switching

TPS27081A: on\off reverse logic

Coby Levy
Prodigy 10 points
Part Number: TPS27081A

Tool/software:

hello everyone,

I cannot figure out why the on\off logic is reversed.

When LOW: VIN = VOUT
When HIGH: VOUT is low.

what do I miss?

VIN is 3.7v lipo battery.

Thanks!

  • 0
    TI__Mastermind 39045 points

    Hi Coby,

    Coby Levy said:
    When LOW: VIN = VOUT
    When HIGH: VOUT is low.

    I don't think this is correct. Even when you don't have R1, pulling ON high should still turn on the main PFET. I think this will help. 

    Best Regards,
    Arush

  • 0 in reply to Arush Gupta
    Prodigy 10 points

    That's what I was also thinking - but this is what I experience,  the logic is reversed.
    When I apply 3.9V (this is my VIN - lipo battery) both to pin VIN and ON/OFF, the output is 0V.

    drives me crazy.

  • 0 in reply to Coby Levy
    TI__Mastermind 39045 points

    Hi Coby,

    I cannot help you much with the information you have provided to me. I would suggest you to do basic things. Kindly follow through them. Please understand that I am suspecting setup related issue here and not the device failing scenario.

    • Firstly check all the connections, supply and load limits and any protection.
    • Check the orientation in which device is soldered.
    • Since you don't have any pullup at R1, I would suggest you to add one. When the ON is low, the nmos is off so gate of Q1 should go to high (due to pullup) and prevent it from turning on.
    • Use external signals to verify the device/PCB functionality. I am not sure if this is possible in your setup.

    Best Regards,
    Arush