- Silicon Laboratories, Inc. Clock User Manual

Si53xx-RM
124 Rev. 0.5
High Reference Frequency
When selecting a reference frequency, with all other things being equal, the higher the reference frequency, the
lower the output jitter. Figures 63 and 64 illustrate this. For a discussion of the available reference frequencies, see
section " Resonator/External Clock Selection" on page 119.
Figure 63. Jitter vs. Reference Frequency (1 of 2)
37 MHz thru 163 MHz Ext Ref, 155.52 MHz in, 622.08 MHz out
-160
-140
-120
-100
-80
-60
-40
-20
0
100 1000 10000 100000 1000000 10000000 100000000
Offset Frequency (Hz)
Phase Noise (dBc/Hz)
Dark Blue—37 MHz
Violet—55 MHz
Light Blue—109 MHz
Yellow-Green—163 MHz