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TPS544C20: Inquiry about Pull-Up/Down resistance value

JH Shin
Guru 10950 points
Part Number: TPS544C20

Hello,

My customer asks about the selection of pull-up/down resistor values for the TPS544C20 control I/O.

What is the appropiate resistance value for the following case, and how to determine it?

  1. 3.3V pull-up on the PGOOD

  2. 1.8V pull-up on the PGOOD

  3. 3.3V pull-up on the DATA, CLK, CNTL and SMBALERT

Thank you.

JH

  • 0
    TI__Guru 56815 points

     

    The selection of the pull-up resistance values for these signals are driven by the system use of these pins, and providing fast enough rise-time for the signals.

    For PGOOD, the sink current should not be more than the specified 5mA test current, and resistances up to 100kOhms can be used is rise-times are not critical.

    For CLK, DAT, and SMBALERT, the sink current should also not be more than 5mA, though resistances of 2.2kOhms are common.  Depending on the number of devices connected to the bus nodes, and the communication bus speed, resistances from 1.1k to 10k are often used.

    The CNTL pin does not have an internal pull-down, and does not require a specific pull-up resistance.  A 10kOhm resistor is more than sufficient to drive the pin "ON" but significantly lower or higher may be used if needed.