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Original question:

TPS54020: question about Ratiometric and Simultaneous Startup Sequence

TPS54020: question about Ratiometric and Simultaneous Startup Sequence

Gayatri Ramachandrran
Prodigy 10 points
Part Number: TPS54020

I would like to use a cpld to power on my tps54020 device.Wrt the same kindly clarify if the following connections are valid.

1)Connecting the pwrgood signal to the cpld so that the cpld can sense the output

2)Driving the TPS54020 device Enable directly from the cpld without using any resistor divider circuitry.

3) Connecting a soft start capacitor on the ss pin.Any other special care required on this pin??

Kindly clarify if extra care is required for any other pins.

Thanks and Best Regards

  • 0
    TI__Guru**** 191445 points
    Gayatri,

    We'll get someone to look at this tomorrow.
  • 0
    TI__Mastermind 35165 points

    Hi Gayatri,

    Please see my comments to your questions below.

    1)Connecting the pwrgood signal to the cpld so that the cpld can sense the output
    I don't see any concern here. The PWRGD pin is an open drain output so make sure there is a pull-up resistor to another voltage source and make sure the pull-up voltage is within the abs max ratings of the TPS54020 PWRGD pin and the cpld.

    2)Driving the TPS54020 device Enable directly from the cpld without using any resistor divider circuitry.
    I don't see any concern here. Just make sure the cpld has enough pull-down strength to hold EN low when you need it to. The EN pin will output a current of 1.15 uA typical when the TPS54020 is disabled and it will output a current of 3.3 uA when the TPS54020 is enabled. Also make sure the voltage forced to the TPS54020 EN pin does not exceed the abs max ratings.

    3) Connecting a soft start capacitor on the ss pin.Any other special care required on this pin??
    All you need on the SS pin is a SS cap to ground to set the desired SS time. Did you have a specific concern here?

    Best Regards,
    Anthony