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Clock Dithering

Rajah
Intellectual 410 points

Hi Guys,

Do you know if Cortex-M3 or M4 support clock dithering? We are trying to get our product qualified for RFI and we are over by 2 dB.


Thanks,

Rajah

  • 0
    Guru 117855 points

    That's one way to reduce emissions - can you repeat your testing while you selectively vary the driven outputs?  Goal is to see if certain outputs are more prone to radiation.  Many devices have some "output slew control" - slewing your output will often reduce radiation.

    Once you identify principal "offenders" - perhaps you can shorten trace lengths or employ some limited shielding.

    Uncertain about clock dithering - techniques described have enabled our group to pass agency testing...

  • 0
    Intellectual 410 points

    Thanks, I will try that out. I was curious because I have used some coldfire micros in the past that had clock dithering feature. We could get anywhere b/w 3-6db down with zero design change,

     

    Rajah