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TXB0108 and ribbon cables

Alexander Templeton
Prodigy 20 points
Other Parts Discussed in Thread: TXB0108, SN74LVC8T245

I'm considering using the TXB0108 not so much for voltage translation as for managing distributed-connection powerup/powerdown issues. BUT I am hearing from the grapevine that these parts are poor in line-driver applications, especially in cabled apps where ringing comes into play.

The spec for load driving is 70pF max before the TXB0108's 10ns one-shot times out. For an unbalanced ribbon cable at 15pF/ft or 4.9pF/dm that works out to 4-2/3 ft or 1.4m max ribbon before trouble starts. So much for theory.

What's the practical limitation for TXB devices and ribbon cables? Any practical experience or gotchas I should be aware of? Do TI offer better alternatives for managing connections between independently-powered systems?

  • 0
    TI__Genius 9085 points

    The auto-direction sensing devices like the the TXB0108 are not intended to drive heavy loads (like feet of ribbon cable.)

    I'm not sure I fully understand your application. You may be asking more of a power question here. But typically i recommend something like the SN74LVC8T245 if your signals are single direction (or you can implement a direction control pin.)