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SN74CBT162292: Effect from Internal Pull Down Resistor

Bhavya Babu
Intellectual 465 points
Part Number: SN74CBT162292

Hi,

In the datasheet of SN74CBT162292, it is mentioned that the part has internal pull down resistors. Iam connecting one voltage divider to this mux .

pull up voltage = 3.3V

Rpull up = 806 ohm

Rpull down = 10K ohm

I need an output voltage of 3V. In this calculation I didn't consider internal pull down of 500 ohm. Shall I consider this also into the calculation , to get correct voltage divider voltage?

Regards,

Bhavya

  • 0
    TI__Intellectual 2900 points
    Hi Bhavya,

    You do not need to consider 500 Ohms internal pull down resistor when desiging your voltage divider.

    The 500 ohm internal pull down is out of the picture when switch is on. It only exisits when switch is off to avoid pin floating.
  • 0
    TI__Expert 3180 points

    Hello Bhavya,

    If the resistor network you're describing matches the one below, where when switch 1 is on, you want to see 3V, then correct, you should not need to take the 500 Ohm internal resister into account.

     Depending on whether you want to see 3V at the terminal A or terminal B, you may want to take into account the Ron of the switch. I have attached a snippet of that table from the datasheet of the SN74CBT162292 below:

    Thank you,

    Louie