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ISOW1044: 2x ISOW1044 on Top and Bottom Layers

Bryan Grant1
Intellectual 370 points
Part Number: ISOW1044

Tool/software:

Hi TI,

Based on space restrictions, I have to place 2x ISOW1044 CAN transceivers on the top and bottom layers directly on top of each other with the circuits physically separated from each other on their own outer layer (with the exception of vias). We only require 60V isolation between the internal signals and the external signals.

Are there any recommendations on whether or not to use the internal layers with local ground pours for the filtered ground on the internal side and the isolated ground on the external side? I am designing an 8-layer PCB, and was planning to use layers 2 and 4 for local ground pours for the top layer transceiver and layers 7 and 5 for the local ground pours for the bottom layer transceiver. Otherwise, I am keeping out any other signals or ground pours between the top and bottom layers.

Thanks for the help,

Bryan Grant

  • +1
    TI__Guru 54155 points

    Hi Bryan,

    Thank you for reaching out.

    As long as you keep all the layers including internal layers clear right under the device, it is fine to route internal layers outside of this region. This is assuming you need your PCB to meet full isolation requirements of ISOW1044. If your isolation requirements are lower then you can have some internal layers under the device while maintain distance betweem them.

    Please see below an example layer stack from one of the other datasheets for more information, thanks.


    Regards,
    Koteshwar Rao

  • 0 in reply to Koteshwar Rao
    Intellectual 370 points

    Hi Koteshwar Rao,

    Thanks for the response. Sounds like the stackup of local ground pours on the proposed internal layers for both transceivers is okay as long as they are outside the area directly underneath the devices.

    To confirm, all internal layers directly underneath the devices (the red dotted area in the diagram) are clear.

    Thanks again,

    Bryan Grant

  • 0 in reply to Bryan Grant1
    TI__Guru 54155 points

    Hi Bryan,

    Your understanding is correct, thanks.


    Regards,
    Koteshwar Rao