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SN74LVC1T45-EP: SN74LVC1T45-EP

Part Number: SN74LVC1T45-EP

I need to know what the recommended value resistor to use as a pull down or pull up on both data lines. This can be referenced on Page 15 of the data sheet.

Thanks,

Paul

  • Paul,
    This can be a fairly weak pullup or down. The purpose of this is to keep an undriven input in a valid state. So, when switching directions, there may be a duration where the translator's input is seeing high impedance. Using pullup or down will pull this signal to a valid level until it is driven. If the system was perfect, and immediately switched both at the same time without contention, then you could argue that a pullup/down was not necessary as the buss is not floating for any significant duration. However, it is conservative to place a pullup or down on each side.
    See this application note
    www.ti.com/.../getliterature.tsp

    In section 4.2, it recommends a 1k to 10k resistor. However, the goal is to not violate the max input transition time. This is in the recommended operating conditions and varies by voltage.

    If this answers your question, please click "Verify it as the answer"
    Regards,
    Wade