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UCC28704EVM-724: Radiated Emission Problem

hüseyin özdil
Prodigy 20 points
Part Number: UCC28704EVM-724

Hello;

We used same circuit and layout with same components with UCC28704EVM-724 board in our system, but we got bad results in radiated emission test. We solwed all frequency without 30MHz but the noise at 30MHz is constantly disturbing the environment. We tried EMI filters, CMM's , Ferrites but none of them worked. When we examine it with the near field probe, the noise seems to be spreading through the transformer. noise continued to spread even when we wrapped the transformer with copper tape. Do you have any idea about this problem?

   

  • 0
    TI__Guru 71335 points

    Hello,

    The UCC28704EVM-724 was tested for conducted EMI and not radiated.  It was never tested for radiated EMI nor did TI claim that id would pass radiated EMI in the EVM documentation. 

    If you need the design to pass radiated EMI you might want to put the design in a metal box/faraday cage and ground the box to chasse ground.  The other thing that you may consider doing is rapping a toroid to the input power cord.  Some times the power cord acts as antenna and this toroid acts as common mode choke.  A lot of power supply designers use these tricks to pass radiated EMI.

    Regards,