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AM26LS33A: pullup/pulldown resistors

Gregory Bain
Prodigy 10 points
Part Number: AM26LS33A


My main concern is that with open input lines and a RT of 120 ohms the output of the driver is 1(high).  This should be a quick answer if I could actually talk to a human and not use email or chat.

  • 0
    TI__Guru 74352 points

    Gregory,

    Thanks for bringing this to E2E.

    So you're saying that your Y output is 1 even when A and B are floating but terminated? If they are floating, that would mean A - B should be between -0.2V and 0.2V, so the Y output is indeterminate. I see the thread is titled pull-up/pull-down resistors, so are you asking if these resistors should be there? Or what value they should be?

    Regards,

    Eric Hackett 

  • 0
    Prodigy 10 points

    According to TIs own data sheet, open lines output a high.  Is this wrong?  Again how do I get to speak to a human?

  • 0 in reply to Gregory Bain
    TI__Guru 74352 points

    Gregory,

    Ultimately it depends on differential voltage between A and B. If they are terminated with a 120 ohm resistor, then that would mean unless something is driving those lines, there should be no voltage drop over the resistor and A and B would be at the same voltage. Open implies that there is no termination resistor present.

    In order to speak to a human, your best bet would be contacting a TI sales office near you and talking to an field engineer there. That person could then get you in direct contact with someone like me who works in the business unit at TI's headquarters.

    Regards,

    Eric Hackett