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SN65HVD1781: D Input Capacitance?

cfranRL
Prodigy 30 points
Part Number: SN65HVD1781

Tool/software:

What is the capacitance of the single-ended input pin D?
I could not find it in the datasheet.

  • 0
    TI__Mastermind 48327 points

    Hi,

    We do not spec the input capacitance on the single ended inputs on most, if not all, our RS-485 devices. 

    Is there a certain range that you need to keep the capacitance under?  because the capacitance shouldn't be very high on that pin (should be single digit pF level )

    Best,

    Parker Dodson

  • 0 in reply to Parker Dodson
    Prodigy 30 points

    Ok I'll assume 10pF.
    My application has a 1kΩ series resistor directly on the input so I needed to verify the bandwidth of the resulting RC lowpass is sufficient.
    SN65HVD1781 is 1MHz max, so the required bandwidth is 3MHz.
    If input pin capacitance is 10pF, then the maximum series resistor would be 5.3kΩ. So 1kΩ should be fine.

  • +1 in reply to cfranRL
    TI__Mastermind 48327 points

    Hi,

    That should be a perfectly acceptable estimation (I honestly think it may be a bit lower than 10pF - but to be on the safe side that should be fine) - between 1k and 4.7k is what we typically see on these lines (for slower devices up to 10k is pretty common) for the pull-up calculation. So I don't see any risk with that.

    Please let me know if you have any other questions.

    Best,

    Parker Dodson