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SN74LVTH241: Design Concept Check

Alfred Oo
Prodigy 30 points
Part Number: SN74LVTH241

Tool/software:

Hi TI team,

I'm using some mux and buffer for JTAG application.

Need TI team to review the application in terms of correctness of part select, pull up/low resistor which concerning about active bus-hold feature.

Thanks.

  • 0
    Guru 278790 points

    Pull-up/-down resistors should not be used together with bus-hold inputs. (Bus hold works like a pull-up or pull-down, depending on the last state.)

    • If the external resistors are stronger than the bus hold, then the bus hold has no effect.
    • If the bus hold is stronger than the external resistors, then the external resistors have no effect.
    • If both have similar drive strength, and if they pull in different directions, then the resulting voltage is invalid.
  • 0 in reply to Clemens Ladisch
    Prodigy 30 points

    Hi Clemens,

    It is always my pleasure to get your review with your expertise and professionalism. Appreciate that.

    If possible, can i get your email as well? Thanks.

  • 0 in reply to Clemens Ladisch
    Prodigy 30 points

    Hi Clemens,

    Let me add some question:

    1. The bus hold feature only applicable for buffer's input side right?

    2. Can you explain more on "If both have similar drive strength, and if they pull in different directions, then the resulting voltage is invalid."? 

    Great thanks.

  • 0 in reply to Alfred Oo
    Guru 278790 points

    1. Yes.

    2. If you have a 10 kΩ pull-up and a 10 kΩ pull-down, then the resulting voltage is VCC/2.