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TPS2491: Floating OUT pin

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?

  • 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
  • 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
  • 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