what is the spread-spectrum clock generator

[engr_joni_ee]

Hi,

I read in a text book "Use spread-spectrum clock generator to spread the first harmonic over a wider frequency range and decrease the radiated energy within the bandwidth of the FCC test.". Any example of spread-spectrum clock generator that can have first harmonic over a wider frequency range ?

 

[barry]

Try this:
1) Buy a computer
2) Turn it on
3) Search “spread spectrum clock generator”
4) Read the 14000000 results.

 

[danadakk]

https://www.infineon.com/dgdl/Infineon-WP0011-ErrataSheet-v01_00-EN.pdf?fileId=8ac78c8c7d0d8da4017d0fb2068a2649

Application Note: AN10005 Spread Spectrum Clock Oscillators

This application note discusses how to mitigate system EMI emanating from the clock and avoid dependence on filtering, shielding, and other costly techniques that consume valuable board space.

www.sitime.com

Regards, Dana.

 

[dick_freebird]

A question to ask yourself is whether playing with "decrease
the radiated energy within the bandwidth of the FCC test"
is going to solve any problem. It's more of a "points shaving"
play, than a "touchdown pass" and it's about compliance to
a spec without actually changing the amout of RFI emitted.

"All you need" is more pull-range on whatever is spreading
the oscillator.

 

[engr_joni_ee]

Yes, a spread-spectrum clock generation is an efficient way to reduce EMI. How do we relate clock from crystals and crystal oscillators ? Are these clocks from crystals and crystal oscillators generated to reduce EMII and using spread-spectrum techniques ?

 

[FvM]

Regular crystal oscillators never implement spread spectrum clocking, only special clock oscillator components.

There are many applications that don't allow for spread spectrum clocking.