EMC - LPC54616J512BD208 spread-spectrum operation

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EMC - LPC54616J512BD208 spread-spectrum operation

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istvanmate
Contributor II

I am starting the layout for a new board using the LPC54616J512BD208. EMC is kind of a blind corner and I am a bit concerned. Is there a checklist or a best practices guide to help control EMC from the start?

In my last design, I had a 93 MHz spike above the limit, radiating from the USB cable and I traced its source to near the center of the micro sitting far away from the USB connection - not an NXP micro btw. I had a home made coax cable probe hooked to the sprectrum analyzer and the signal was strongest when I hovered near the center of the micro. I had nothing coming out of the micro near that frequency yet the USB cable behaved like it was hooked directly to this mysterious internal module in the micro doing its thing at 93 MHz. The micro user guide was over 1200 pages but almost nothing regarding EMC. Plenty of guidance on everything except EMC. For those who are lucky enough to have an RF guy on the team it might not be a problem but for most designers EMC guidance at par with today's EMC requirements would be very helpful. 

Coming back to the LPC54616J512BD208, can a spread spectrum oscillator be used to spread the RF energy? 

 

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xiangjun_rong
NXP TechSupport
NXP TechSupport

Hi,

Unfortunately, the on-chip PLL module of LPC54616  does not support frequency spreading feature, so you have to use the other method to reduce the EMC instead of using spreading frequency clock.

Hope it can help you

BR

XiangJun Rong

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xiangjun_rong
NXP TechSupport
NXP TechSupport

Hi,

Unfortunately, the on-chip PLL module of LPC54616  does not support frequency spreading feature, so you have to use the other method to reduce the EMC instead of using spreading frequency clock.

Hope it can help you

BR

XiangJun Rong

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istvanmate
Contributor II

Thanks for the clarification. 

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