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Original question:

ISO5452

ISO5452: What is the value of internal Pull-down resistor and pull-up resistor?

Eggsy Pang
Expert 4985 points
Part Number: ISO5452

Hi team,

         As we known, in ISO5452, there are internal Pull-down resistor in IN+ pin and internal pull-up resistor in IN- pin.

        What is the resistors’ value of  internal Pull-down resistor and pull-up resistor? We can’t find in the datasheet.

Do we need add external resistor between IN+ pin and IN- pin? Because there are internal Pull-down and pull-up resistors, I think it don't need add external resistor between IN+ pin and IN- pin. But why do some boards still need add it ?

Could you have any idea and suggestions?  Thank for your help! 

  • 0
    TI__Intellectual 1665 points
    Hi Eggsy,

    The value of internal pull-up and pull-down resistors is between 40k and 100k across PVT corners.

    With Regards,
    Xiong
  • 0 in reply to Xiong Li
    TI__Expert 4985 points

    Hi Xiong,

              Customers tested the the internal pull-up and pull-down resistor value and the value is about 400K.

    May I know if something is wrong? Testing way or others?

    BTW, as you said, the internal pull-up and pull-down resistor value is between 40k and 100k across PVT corners. Why the values is so wide different? Will it cause some problem?

    Thanks!

  • 0 in reply to Eggsy Pang
    TI__Intellectual 1665 points

    Hi Eggsy,

    You can add a pull-down resistor on the IN- and a pull-up resistor on the IN+. Those resistors would form voltage dividers with internal pull-up and pull-down resistors. You can measure the voltage on the IN+ and IN- pins. Please not actively drive those pins during the tests.

    The internal pull-up and pull-down resistors are intended to be used to position IN+ and IN- pins to defined states. The value does not need to be very accurate. It is common for on-chip resistors to have that wide range.   

    With Regards,

    Xiong