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ISO1540: Using ISO154x for isolating RS485 bus

Eran Shternlib
Intellectual 1020 points
Part Number: ISO1540
Other Parts Discussed in Thread: ISO1452, ISO1450

Hello team,

 

Is it possible to use those ISO154x bidirectional I2C isolators for isolating other communication protocols which are not I2C ?

Specifically I thought to use it for isolating RS485 bus..

 

Thanks 

  • 0
    TI__Expert 8030 points

    Hi Eran,

    Thanks for reaching out. 

    No, it is not possible to use the the ISO154x to isolate an RS-485 bus. RS-485 is a protocol that uses differential signaling, and as a result all RS-485 transceivers are specifically designed to send and receive differential signals that are at voltage levels specific to RS-485. I2C uses standard 0-5 V logic voltage levels for communication. Any I2C isolator is specifically designed to support 0-5 V logic level signals, which means that they cannot be used to send a receive signals that are both differential and at different voltage levels (the common mode range of an RS-485 bus can be anywhere from -7 to 12 V). Therefore, the ISO154x cannot be used to isolate an RS-485 bus.

    To isolate an RS-485 bus, we recommend that you use devices from out latest isolated RS-485 transceiver family (ISO14xx), such as the ISO1450 or ISO1452.

    Regards,

    Kenneth