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ISOW1412: current of termination resistor

Part Number: ISOW1412

Hi team,

My customer is considering to use ISOW1412 with half duplex configulation.

My customer wants to know the maximum current which go through the termination resistor: Rt.

In general RS485 communication, I guess common mode voltage range is from 7V to 12V.

Is the maximum voltage applied to the termination resistor also 12V?



  • Hi Ohashi-san,

    Thanks for reaching out.
    Since the termination resistor is connected across the differential pair of RS-485 bus, the current through termination resistor is only determined by the differential voltage and the common-mode voltage doesn't impact the current into this resistor.

    The maximum differential output voltage can be upto the voltage applied to VISOIN, the maximum current through termination resistor can be expressed as below.

    IR(max) = VISOIN / RT

    where RT is the termination resistor.

    Let me know if you have questions, thanks.

    Koteshwar Rao