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Non Isolated RS-485 vs Isolated RS-485

Matthew Xiong
Prodigy 595 points

What's the difference between isolated RS-485 and non isolated RS-485? Do we have specific transceivers for both? 

  • 0
    TI__Expert 6955 points
    Hi Matthew,

    Isolated RS-485 has an isolation barrier that will physically separate the input and output side of the transceiver. TI achieves this using carefully designed capacitor stages. Isolation protects the system from being exposed to high voltages through the inputs or outputs. Non-isolated RS-485 simply does not have this barrier. There are several transceivers available for both isolated and non-isolated RS-485 transceivers available for both full and half duplex.

    -Lucas
  • 0 in reply to Lucas Schulte9
    TI__Prodigy 595 points

    Hi Lucas,

    Thanks for the response. Do you have any appnotes, or collateral that I can read to familiarize myself with the basics of isolation? If high voltage or high current is the issue, could an OVP or current limit switch do the job just as well? When would you be using iso vs these other protection devices?

  • 0 in reply to Matthew Xiong
    TI__Expert 6955 points

    Isolation University.xlsx

    Matthew,

    I have attempted to include an excel sheet from the Isolation Department's ISO University. It contains several links to collateral explaining isolation and it's applications. If the attachment failed, type "iso/" in your browser and click on the ISO University link. Simple current limiters or OVP devices do not solve the complete task of isolating signals and overcoming ground loops found in industrial systems. There's more to it than just protection. 

    -Lucas