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ISO1430: ISO1430 - Separate ground ISO1430 from ground shield wire - 61000 4-4

bruno lepvraud
Prodigy 70 points
Part Number: ISO1430
Other Parts Discussed in Thread: ISO1410

Hello,

We used an old  bus based on RS485, and upgrade our equipment  to use ISO1430 which works perfectly. We have a doubt about ground, because  the "shield wire" is connected to DB9 on our equipment to ground throughout a capacitor and varistor, to have a network to the same equipotential.

To have good 61000 -4-4 tests, should we connect the ground of ISO1430 via the capacitor and varistor (see image, solution 1?), or should we isolate the grounds of the ISO1430 and connect them directly to the ground (see image, solution 2?)

Regards, Bruno

  • 0
    TI__Mastermind 22115 points

    Hello Bruno, 

    Allow me a few days to reach out to the team and gather this information. Iin general, we do not recommend connecting components across the isolation barrier. 

    The pictures you have shared are blocked. Please provide screenshots to use in further posts. 

    Best,
    Andrew

  • 0 in reply to bruno lepvraud
    TI__Guru 54275 points

    Hi Bruno,

    The RS-485 shield wire connection to system ground either directly or through capacitor/varistor doesn't have direct impact on device operation. Therefore, this is not a concern for ISO1410.

    For optimum protection, the shield wire should be connected to the chassis of the end-equipment. If chassis is on the left side (as shown in the block diagram), you should connect shield to left ground through capacitor/varistor. If chassis is on the right side, then you can connect shield directly to right ground.

    Please note that GND2 pin of ISO1410 should connect to system ground directly and not through capacitor or varistor. Thanks.


    Regards,
    Koteshwar Rao

  • 0 in reply to Koteshwar Rao
    Prodigy 70 points

    Hello thanks for answer. See new image (i correct earth and ground), is it correct ? You mention that GND2 is connect to ISO ground directly.  And from ground to earth, should we add protection components for hard environment ?

    Regards, Bruno

  • 0 in reply to bruno lepvraud
    Prodigy 70 points

    Please note there is only 1 schem to see (i probably download twice by error).

  • 0 in reply to bruno lepvraud
    TI__Guru 54275 points

    Hi Bruno,

    The GND2 of ISO1410 should be connected to ISO Ground directly, I see you have already done that. Since ISO Ground isolated from the System Ground, it should be connected to the chassis through the capacitor / varistor network. Thanks.


    Regards,
    Koteshwar Rao

  • 0 in reply to Koteshwar Rao
    Prodigy 70 points

    Hello, 

    Thanks for your answer. Ok  we connect  1430 ISO ground with the same ground of wire (see image).  But my fear, if we have electricals perturbations on wire during EMC tests, will it damage/perturbations quality of ground of ISO1430 ?

    Regards,

    Bruno.

  • +1 in reply to bruno lepvraud
    TI__Guru 54275 points

    Hi Bruno,

    Thank you for sharing the updated block diagram with new connection. Considering the fact that the RS-485 bus is protected using TVS diodes, this shouldn't be an issue.

    All the diagrams that you have shown so far are not wrong, you would need to understand which part of the system connects to chassis directly and then everything should connect to it through a capacitor/varistor.

    The previous diagram that you shared (see image below) is also sufficient by itself. You can probably go with this approach and it should work fine. Thanks.


    Regards,
    Koteshwar Rao