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USB low-full-high speed peripherals

eran
New Contributor

Hello

I ran an radiated RF emission test, and got a 216MHz noise from the CY7C68014A. The crystal frequency is 24MHz and the PLL microcontroller can increase the clock frequency up to 480MHz. How can I overcome this noise?

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1 Solution
MallikaK_22
Moderator
Moderator

Hi,

Could you please check High-Speed USB PCB Layout Recommendations in the App Note: https://www.cypress.com/file/135006/download

Regards,

Mallika

Mallika

View solution in original post

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zzz_3221081
New Contributor II

I am more of a SW guy, but I couldn't help but notice that 24 * (2 * 2 * 2) + 24 = 216, the frequency you measured.

Probably a mixing of the third harmonic with the base frequency.

From my limited HW design knowledge I gathered, the source is often the supply lines, less often driven IO lines. Perhaps you need to add some RF filtering.  Buffer caps (electrolytic caps) are very bad at this.

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MallikaK_22
Moderator
Moderator

Hi,

Could you please check High-Speed USB PCB Layout Recommendations in the App Note: https://www.cypress.com/file/135006/download

Regards,

Mallika

Mallika

View solution in original post

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