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TPS3808G01-Q1 's VIT resistor needed or not？

Jacky Chen29
Genius 4735 points
Other Parts Discussed in Thread: TPS3808

Hola,

Do we need to put a VIT resistor as below location？

According to the datasheet description and it needs to use dividing resistors to calculate VIT resistor what value should be put, but the question is that I'm not using

dividing resistors to set sense threshold voltage because of I'm connect SENSE pin to VDD directly.

And we assumed that we don't need to put VIT resistor in our circuit but I found one issue when we tested our board, there is a pulse if we didn't put

VIT resistor, but the pulse will be disappeared when we connect VIT resistor between VDD and RESET pin.

My question is that should we need to put this pull up resistor between VDD and RESET pin？but why？we don't have dividing resistors in our circuit.



  • 0
    TI__Genius 16030 points
    Hello Jacky,

    The resistor from RESET to VDD is the pull-up resistor for the RESET pin. In TPS3808, RESET is an open drain signal, so it needs an external pull-up to drive the RESET pin high. This pull-up resistor should be between 10kohm and 1Mohm. Do you already have some pull-up resistance on the RESET line of the TPS3808? If it's not external, it could be a pull-up internal to the chip which has this reset pin as an input.

    It may be confusing that the formula for VIT is located by the pull-up resistor. But the formula uses R1 and R2, which are the resistors from SENSE to VDD and GND. You don't need to use those dividing resistors - in that configuration, it means TPS3808 will trigger a reset at 0.405V.

    Regards,
    Karl
  • 0 in reply to Karl Wallinger
    Genius 4735 points
    Hola Karl,
    Thank you very much for your prompt reply and it's helpful.