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TPS2491: Floating OUT pin

Craig Newbold79
Prodigy 20 points
Part Number: TPS2491

I have a design that has accidentally left the OUT pin disconnected.   The Input voltage to the TPS2491 and the FET it controls is 12V.   The PG signal is used to switch a DC/DC supply that follows the FET.

The PG signal still functions despite the OUT pin disconnected and what I am seeing is that the OUT pin is floating at around 13.6V.   Is that normal, should the part function if OUT is disconnected and would it always tend to float at this high voltage?

  • 0
    TI__Guru** 105611 points
    Hi Craig,

    As the MOSFET is already fully enhanced, the PG output stays HIGH and continues to remain HIGH till VDS exceeds 2.2V.

    Best Regards,
    Rakesh
  • 0 in reply to Rakesh
    Prodigy 20 points
    Hi Rakesh - thanks for your response. In my situation where the OUT pin is not connected to the FET's source I am not sure how the part can determine that Vds is above 2.2V. On the modules I have checked the floating OUT pin is usually around 13.6V while the Input to the External FET is 12V. But I am not sure if this would always be the case, or is it possible that the PG may go low and turn off my DC/DC converter?
    Regards - Craig
  • 0 in reply to Craig Newbold79
    TI__Guru** 105611 points
    Hi Craig,

    It is hard to confirm the potential and the state of OUT pin when it gets disconnect from the system and therefore PG signal status also. The parasictics at Vout pin can hold its earlier potential and can keep PG signal HIGH.
    Do you expect this to happen in your system? why?

    Best Regards,
    Rakesh