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Auto direction sensing translator to connect to NI DIO card

Bhavya Babu
Intellectual 465 points
Other Parts Discussed in Thread: SN74AVC2T245

Hi,

Can you suggest any auto direction sensing level translator to connect with NI DIO card?

Regards,

Bhavya

  • 0
    TI__Mastermind 30545 points
    Hello Bhavya,

    Can you provide us with a little more information? What voltage levels will you be translating to/from? What frequency will you be operating at? Which DIO card will you be using? Thanks.
  • 0 in reply to aozer
    Intellectual 465 points
    Hi,

    I want to translate from 1.8V to 3.3V. The maximum frequency should be greater than 50MHz.
    Iam planning to use PXIe-6544.
    Please suggest some auto direction sensing buffers for the above application.

    Regards,
    Bhavya
  • 0 in reply to Bhavya Babu
    TI__Mastermind 30545 points

    Hi,

    We do not have any auto direction translators that can operate over 50MHz at that voltage. You may want to look into the LSF family of translators. They are bidirectional translators that don't need a direction control pin.

  • 0 in reply to aozer
    Intellectual 465 points

    Hi,

    Iam going to use a cable which has 100pF capacitance. The datasheet of the cable is attached with this mail.

    I have the following queries:

    If Iam using SN74AVC2T245 buffer at 12mA drive strength for 3.3V, whats the maximum frequency/ rise time that I can drive through the cable if my trace capacitance is around 3pF?

    Regards,

    Bhavya 

  • 0 in reply to Bhavya Babu
    TI__Mastermind 30545 points
    Rounding total capacitance to 110pF we can find a rough estimate for the rise/fall time and frequency using the equation I = C * dV/dt.

    rise time = dt = C * dV/I = 110pF * 3.3V / 12mA = ~30ns.

    Assuming rise time = fall time you can then estimate the maximum frequency

    F = 1/(tr + tf + th + tl)

    where tr and tf represent the rise and fall times, th represents the high period of your signal and tl represents the low period of your signal. The minimum values of th and tl will be dependent on your protocol but if we substitute in 20ns for th and tl this will result in a maximum frequency of 10MHz.