• State
  • Locked Locked
  • Replies 1 reply
  • Subscribers 33 subscribers
  • Views 3185 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

DP83848 Bob Smith

Mohamed Hellal
Intellectual 2295 points

Hello,

My customer would like to perform all emissivity tests but in my opinion if they will need to improve the behavior of the PHY by adding extra filtering in the Data lines of the ethernet bus to perform all the tests specially because one ethernet communication is used when the vehicle is running.

Do you have any application notes/hint for the extra filtering on the Data lines of the ethernet bus. Also any recommendation of components reference for this filter?

Thank you, 

Mohamed 

  • 0
    TI__Mastermind 18425 points
    Hi Mohamed,

    Please ensure that the transformer meets the requirement as mentioned in www.ti.com/.../snla079d.pdf Place the transformer such that the Common mode chokes are on the cable side. There should be no metal beneath the transformer on any layers. The signal traces should be differentially coupled before and after the transformer with 100ohm diff impedance. The pull-up resistors (49.9ohms) used on the data lines should be 1% tolerance. The 75ohm resistors on the bob smith termination should be relatively large in size 0603 or 0805. This does not affect emission but helps with immunity. The capacitor in Bob Smith termination should be high voltage rate for e.g. 2kV. I will also recommend including space for extra de-coupling caps on the center tap of the transformers to GND.

    We have a reference design which has good EMI EMC performance: www.ti.com/.../tida-00207
    You can refer to the schematics for more information.

    -Regards,
    Aniruddha