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LP87725-Q1: RSTOUT open-drain configuration and voltage tolerances

Taylor Gage
Prodigy 200 points
Part Number: LP87725-Q1

Tool/software:

I'm working on a design using LP87725-Q1 and would like to use the RSTOUT pin pulled up to 1.8V instead of 3.3V. The RSTOUT pin says it can be open-drain if the internal PU resistor is disabled, which should allow me to do this. What is the default state of that pin with regards to being open-drain vs push pull? And if it's not OD by default, what do I need to do to make that happen? Thank you!

OPN: LP87725110RAGRQ1

  • 0
    TI__Genius 14310 points

    Hi Taylor,

    The correct OPN ; LP87725101RAGRQ1 , there must be typo in the schematic.
    nRSTOUT: It is configured as OD with internal PU resistor enabled and polarity is active low.
    Internal it is pulled up to 3.3 V level so when you measure the voltage on the pin in inactive condition you would observe 3.3V.
    The default state is HIGH meaning there isn't any error pending. If there would be any error which is supposed to cause nRSTOUT to trigger then the signal would be LOW (~0 V).
    With this default configurations, you do not need to pull this up to 1.8 V .

    Regards,

    Ishtiaque 

  • 0 in reply to Ishtiaque Panhwar
    TI__Prodigy 200 points

    I see. If my goal is to make the RSTOUT signal 1.8V based, could I use the register setting for NRSTOUT_PU_EN to forcibly disconnect the internal pull-up resistor and pull it high to 1.8V externally?

  • +1 in reply to Taylor Gage
    TI__Genius 14310 points

    Hi Taylor,

    Yes It needs to be disconnected then externally connected to 1.8V. 

    Regards,

    Ishtiaque