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TUSB211: Best Layout Practices -- EMI

SSF
Intellectual 2025 points
Part Number: TUSB211

Hi Team,

I have a question on best layout practices for TUSB211, related to EMI. My customer is using a Common Mode Choke (CMC) between the PCB digital ground and the USB cable “chassis” ground. They are now in a situation where the DATA+/- lines will cross those two ground domains and potentially generate noise in their system going up through the USB cable.

We'd appreciate any guidance on the best way to handle this.

Thanks!

  • 0
    TI__Mastermind 36085 points
    Hello SSF,

    Please use the following links for full reference, the common layout guidelines for EMI are:

    • Place ESD and EMI protection devices as close as possible to the connector.
    • Keep any unprotected traces away from protected traces to minimize EMI coupling.
    • Incorporate 60% voids under the ESD/EMI component signal pads to reduce losses.
    • Use 0402 0-Ω resistors for common-mode filter (CMF) no-stuff options because larger components will typically introduce more loss that the CMF itself.
    • Place any required signal pair AC coupling capacitors on the protected side of the CMF and as close as possible to the CMF.
    • If vias are needed to transition to the CMF layer, ensure that the vias are as close as possible to the CMF.
    • Keep the overall routing of AC coupling capacitors + CMF + ESD protection as short and as close as possible to the connector.

    www.ti.com/.../spraar7f.pdf
    www.ti.com/.../scaa082.pdf

    Best regards,
    Diego.