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SN65HVD72: can we use 3.3V supplied SN65HVD72 and 5V supplied SN65176 in the same system?

Howard Zou
Genius 12365 points
Part Number: SN65HVD72

Hi,

can we use them in one system?

Is the configuration below acceptable? Personally I think we should remove the pull up and pull down resistors on A and B and then it would be okay.

  • 0
    TI__Guru 62920 points

    Howard,

    You are correct.  Both transceivers are compliant to TIA/EIA-485 and will be interoperable with one another regardless of the supply voltage.  However, if pull-up resistances are used on both sides then there could be current flow from the higher-voltage to the lower-voltage rail.  You could avoid this by placing the biasing resistors only on a single node.  Alternatively, you could place a diode in series with the 3.3-V pull-up resistance in order to prevent backwards current flow.

    Please let us know if you have any further questions.

    Regards,
    Max