PL607041 Datasheet, PDF (3/11 Pages) Micrel Semiconductor – ClockWorks® PCIe Quad Outputs Ultra-Low Jitter, HCSL Frequency Synthesizer

Micrel, Inc.
EMI Reduction
The Spread Spectrum modulation causes the emission of
spectral components in the clock signal to be reduced. The
spectrum plot on the right shows measurement results with
the two spread settings versus no spread. This plot is
looking at the 11th harmonic in a 100MHz clock, at
1.1GHz. The scale is normalized to the strength of this
spur without spread. The plot shows about 21dB reduction
for -0.25% spread magnitude and 24dB for -0.50% spread
magnitude.
The plot also shows how the frequency spreading is
happening downwards.
PL607041
April 1, 2014
3
Revision 1.2
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