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TPS22919: Series current limit resistor

high speed guy
Expert 3505 points
Part Number: TPS22919

Hi,

When interfacing between low voltage control logic (3.3V, 2.5V) and higher voltage devices I generally include a series current limit resistor (1K Ohm typical) to prevent logic high overcurrent in the case of higher voltage device failure or supply failure. The TPS22919 has an input active pull down circuit, is that compatible with this approach?

Thanks, 

HSG

  • 0
    TI__Genius 15760 points

    Hi HSG,

    Can you elaborate on the use case where you think this will be a problem? I will say that while the input does not have an active pulldown, the ON pin has one that keeps the voltage on the pin pulled low. In the case of overvoltage, this pulldown does not protect the pin. Each pin has an ESD diode that will be damaged once there is an overvoltage event on the pin, and the pulldown will not prevent this.

    Thanks,

    Alek Kaknevicius

  • 0 in reply to Aleksandras_Kaknevicius
    TI__Expert 3505 points

    HI Alek,

    The use case is varied however what I really like to know is the use of  a series resistor going to negatively impact the pull down circuit?   If so, can you explain why?  If not, do you have any general precautions?

    Thanks,

    HSG

  • 0 in reply to high speed guy
    TI__Mastermind 32650 points

    Hey HSG,

    Under the assumption that you place a 1KOhm resistor between the controller and the ON pin of the switch, we do not expect you to run into any issues with the smart pull down.

    The max leakage into the ON pin is 100nA. If you use a 1kOhm resistance, you will have a 100uV drop across the limiting resistor in the worst case.

    I think your approach is fine and the part should behave correctly.