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TPS1H000-Q1: TPS1H000-Q1 Open-Load Detection Pull-up

Gaston Schelotto
Expert 2860 points
Part Number: TPS1H000-Q1

Hi,

Page 16 of TPS1H000-Q1 datasheet shows the method for Open-Load Detection when Output Off.

If the pull-up resistor is placed, there will be a current that will circulate through it when Output is On. Correct?

In my case the load is a LED indicator so during the TPS1H000 power-up the LED will flash until the default Off state is achieved. Is my assumption correct? 

If so, how could I avoid this LED flash during power-up?

regards,
gaston

  • 0
    TI__Mastermind 35035 points

    Gaston,

    When the output is on you can look at this like two parallel resistors: the 15kohm external pull-up and the 1ohm on-resistance of the FET. While a miniscule amount of current might flow, the low impedance path will be through the switch and what flows through the resistor will be negligible.

    Is the worry that in the off state that enough current will flow through the resistor so that the LED biases in the OFF state?

  • 0 in reply to Timothy Logan
    Expert 2860 points
    Timothy Logan said:
    Is the worry that in the off state that enough current will flow through the resistor so that the LED biases in the OFF state?

    Exactly. Could this happen and make the LED light?

  • +1 in reply to Gaston Schelotto
    TI__Mastermind 35035 points

    Gaston,

    The pull-up resistor on the output is generally 15k. This would limit the current that ultimately goes to the LED and likely not give it enough current to actually turn on. Say the LED draws 500mA of current... on a 12V supply (with the switch enabled) that would be approximately at 24ohm resistor. Now thing when the device off there is essentially a 15k resistor in series with a 12ohm resistor meaning the current draw would only be approximately 0.79mA  (15.024kohm) and the LED would likely not turn on.