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SN65LBC176: Some question for RS422 application

Tiger Yeh
Expert 4275 points
Part Number: SN65LBC176
Other Parts Discussed in Thread: SN75176A,

Hi,

RS422 and RS485 are electrical characteristics compatible, I have some questions below.

1. If SN65LVC176 datasheet is not mentioned RS422, could it use for RS422 application?

2. Is it okay to use UART to direct drive SN65LBC176 or SN75176A for RS422 application?

Thanks and Best regards,

Tiger

  • +1
    TI__Mastermind 43265 points

    Hi Tiger,

    So first RS-485 devices can generally support RS-422 but RS-422 specific devices cannot do RS-485. RS-485 is mostly backwards compatible with 422 but they aren't interchangeable. 

    For your specific questions:

    1. Yes  - but there is some risk. the SN65LBC176 should meet all the RS-422 specifications - but there is no specification for VOD with a  termination resistor of 100 Ohms (RS-422 standard) - which should be a minimum of 2V for RS-422 applications - typically if it meets the RS-485 54 Ohm loading conditions it should also meet RS-422. So yes but the output isn't guaranteed to be a minimum of 2V at a 100 Ohm load and it isn't directly spec'd for RS-422 (most of our RS-485 devices are spec'd for both - I am not sure why we decided not to include that spec with this device).

    2. Are you asking if you can interface a controller and transceiver and have UART signals run between the controller and transceiver? If that is the case - the only requirement is that the logic inputs (D and enables) are at proper voltage levels for their respective high and low voltage inputs - generally a direct controller to transceiver connection for UART signals is the most common use when looking at RS-4XX parts and UART. But if I have misunderstood anything please let me know and  I will see what I can do!

    Best,

    Parker Dodson