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THVD2410: Is THVD2410 and SN65HVD1786 compliant to V.11/X.27?

Walter Ahrend
Intellectual 990 points
Part Number: THVD2410
Other Parts Discussed in Thread: AM26LV31E

Tool/software:

The datasheets of both devices do not mention any compliance to V.11/X.27...

The customer wants to know if these two devices implicitly comply to these standards without any citation in the datasheet?

In case NOT, which modern devices DO comply to these standards?

  • 0
    Guru 272640 points

    V.11/X.27 are the standards that define RS-422.

    RS-422 and RS-485 have somewhat different electrical characteristics, but you can RS-485 transceivers in RS-422 systems, so all modern chips are designed for RS-485.

    (Some old chips like the AM26LV31E implement only RS-422. But you would use them only if you actually had a matching number of fixed-direction channels.)

  • 0
    TI__Guru 56900 points

    Hi Walter,

    Clemens is correct the V.11/X.27 just refer to the RS-422 standard. The main difference between the RS485 standard and the RS-422 standard is the voltage drop across the load requirement and a limitation on the amount of devices on the bus (32 unit loads vs. 10 max). RS485 generally uses a 60 ohm termination resistor, but the standard requires you assume it's 54 ohm (10% tolerance in the negative direction). The voltage drop across the 54 ohm load is required to be 1.5V minimum. For RS-422 I believe they use 100 ohms with a minimum of 2.2V. The RS-485 definition is harder to pass than the RS-422 so by default RS485 drivers are able to drive 100 ohm loads and meet the RS-422 requirement for voltage across the termination resistor. 

    Short answer is, if it passes the RS-485 standard then it passes the RS-422 standard.

    -Bobby