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ISOW1412: ”Keep-out zone for any metal” on layout

Shotaro Sakai
Intellectual 2970 points
Part Number: ISOW1412
Other Parts Discussed in Thread: ISOW7741

Hello team,

For a two-layer board (double-sided board), is it better to remove metal from the area on the B-side (A-side: ISOW1412BDFMR)?

Best regards,

Shotaro

  • 0
    TI__Guru 54765 points

    Hi Shotaro-san,

    Thank you for reaching out.

    By B-side, I am assuming that you are referring to GND2 side. If you are referring to removing GND polygons in the PCB, it is upto customer whether to keep the polygons or not. These polygons do not impact ISOW1412 provided they are not overlapping into the area marked by a line at VISOOUT and GND2 pins.

    If i have misunderstood your question, then please help clarify your question further for me to better understand. Thanks.


    Regards,
    Koteshwar Rao

  • 0 in reply to Koteshwar Rao
    TI__Intellectual 2970 points

    Hi Rao-san,

    Thank you for supporting. Let me double check my understanding.

    Even if GND2 exists on bottom layer, we need to design with no overlapping into the area marked by green line. Is it right? The below figure comes from a EVM layout.

    Best regards,

    Shotaro

  • 0 in reply to Shotaro Sakai
    TI__Guru 54765 points

    Hi Shotaro-san,

    Thanks for clarifying. Yes, your understanding is correct.

    The idea is to keep the GND2 pin and the ferrite bead filtered GND separate. Any cross-over of either layer onto each other could render the ferrite bead not useful. This is the reason why we do not recommend crossing-over these layers either on top or bottom layers. Please refer to the below brief tech note that describes this in more detail and also talks about other PCB layout guidelines.

    The document refers to ISOW7741 but is equally applicable to ISOW1412 as well. Let me know if you have any further questions, thanks.

    How to Meet CISPR 32 Radiated Emissions Limits With ISOW7741


    Regards,
    Koteshwar Rao