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AM26LV32: Single-ended input signal

Narek
Prodigy 235 points
Part Number: AM26LV32

Hello,

I would like to know if this device will behave as expected if instead of a differential signal, a single-ended signal is supplied on the "A" input while the "B" input is left floating.  This device is being used on a motor-controller board to accommodate differential Hall signals from an encoder.  However, some encoder only supply single-ended Hall signals, so it would be nice if the same receiver can be used for both signal types.  Since the A and B inputs are internally biased it seems to me that floating the B input is OK so long as the VIT+ and VIT- specifications are met.  If B cannot be left floating, should it be pulled up or down and by what resistor value?

Thanks,

Narek

  • +1
    TI__Guru 50795 points

    Hi Narek,

    While a solution like this is possible, it does not seem ideal as this implementation would lose the benefits of a differential signal. The single ended signal would be much more susceptible to noise, ground shifts, and have worse emissions performance. Ideally a differential signal driver would be included where the single-ended signal originates to carry the signal through the transfer medium as a differential pair. 

     If a single ended solution is to be used, I would recommend tying the unused B pin to an intermediate value, ideally Vcc/2 so that the differential created between it and the A pin will be equivalent for both bit states (~±2.5V). Do note that because this is not the intended use case for the device, unexpected behavior may occur as the operational conditions may deviate from expected norms. 

    Let me know if you have any more questions.

    Regards,
    Eric Schott

  • 0
    Prodigy 235 points

    Understood, Eric.

    Thanks so much!