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TPS54620: Holding EN Low

Russell Wetherley1
Expert 4255 points
Part Number: TPS54620

Hello E2E,

My customer needs to ensure that EN is held low until a micro enables the TPS54620.  However the micro is powered up after 12V is applied to TPS54620.  They want to add in a pull down resistor to hold the EN line low, however, they are curious as to how they should size the resistor.  Do you have any suggestions on the value to resistor to use?  They are open to other methods to ensure that the TPS54620 is held low until the micro enables it.

Also, the micro is using a push/pull output and I can across this thread discussing the need for a protection resistor in series: 

http://e2e.ti.com/support/power-management/f/196/p/454315/1637023?tisearch=e2e-sitesearch&keymatch=TPS54620%25252525252520enable#1637023

Thanks!

Russell

  • 0
    TI__Mastermind 35165 points

    Hi Russell,

    To ensure the TPS54620 stays disabled, the pull down resistor should be less than 830 kΩ to keep the EN pin voltage below the minimum enable voltage threshold with the maximum EN pull-up current. I reviewed our char data to get min/max values for the specifications that matter in calculating this resistance so no additional margin is needed.

    However, once the TPS54620 is enabled the pull-up current is increased. If the pull down resistance needs to be capable of turning the part off after it has turned on, it should be less than 200 kΩ.

    In my experience with this part, I don't know of any reason the series resistor would be required but it wouldn't hurt to at least have a 0 Ω in series. I have always driven the pin directly. Not exceeding the voltage rating is the main thing to pay attention to.

    Anthony