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ISOW1412: ISOW1412 protection against surge transients.

Part Number: ISOW1412
Other Parts Discussed in Thread: THVD1400,

Dear Experts,

I want to ask about protection of RS485 devices. We will have two RS485 communication, one for the internal bus among cards and second one for communnication with external world which may be a high voltage outdoor auto-recloser in the 33KV gantry.

In the datasheet of the device "THVD1400" it recommended adding TVS (or MOV for higher voltages) while the datasheet of "ISOW1412" didn't recommend the same.

So, my question is: Do we need to add TVS or MOV for the "ISOW1412" which will be used for communication with outdoor devices?


  • Hi Mohammad,

    Thank you for reaching out.

    Surge transients on the RS-485 bus typically require external protection as you noticed in the THVD1400 datasheet. Please refer to the below reference diagram that describes various methods to protect RS-485 bus against external transients. Based on your protection requirements, you might have to choose on or more protection components. Let me know if you have any questions, thanks.

    Koteshwar Rao

  • Hi Koteshwar ,

    Thanks for your reply and for the helpful link, I will check it carefully.

    For internal bus I will add only ferrite beads and TVS with pulse proof resistor but I will use all in the RS485 to outdoor connection.