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AM26LV32C A & B floating voltages

Brian Fair
Prodigy 250 points

Other Parts Discussed in Thread: AM26LV32E

With a 3.3V supply voltage, I'm measuring the A inputs to be 1.73V and the B inputs to be 1.48.  I don't completely understand that because the datasheet equivalent input circuits show A and B being the same.  I have a feeling it is like that on purpose because of the +/- 200mV sensitivity of the part.  Will those voltages be consistent from part to part?


Here is what I'm trying to do.  I want to set the B input to a constant voltage.  I want to connect the A input to an AC coupled clock signal (48KHz-192KHz) such that I obtain the max sensitivity.  With the measurements I took above, that would mean that I set the B input to 1.73V.  I just don't know if those voltages will be consistent from part to part.


Thanks,

Brian

  • 0
    TI__Guru**** 170776 points
    Brian,

    It took a while to answer because by today's standards AM26LV32C is not high speed. Faster response will be in the industrial interface forum.

    Do you need all four channels?
    If not, then you can buffer the voltage at an unused A input using an op amp to provide voltage to the B input on used channels.
    If all are needed, then you could low pass filter a clocked A input and buffer that to the "B" input.
  • 0 in reply to Ron Michallick
    Prodigy 250 points
    Ronald,

    Understood on possible solutions but I still am wondering why the A inputs and B inputs are measuring different voltages if the datasheet shows equivalent input circuits for A and B to be the same. Will those voltages be consistent from part to part? Is there a spec?

    Thanks,
    Brian
  • 0 in reply to Brian Fair
    TI__Guru**** 170776 points
    Brian,

    It is standard that there is a internal pull-up on A and a pull-down resistor on B for fail safe operation.
    It is odd that this one data sheet failed to show these resistors. You could try AM26LV32E which shows the resistor.

    There is no specification for the voltage or its tolerance. You add external divider which will lessen the effect of internal variances.
    The only thing I can say for sure is +/-200mV differential will be decode as output low and high.