Si53xx-RM

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.

37 MHz thru 163 MHz Ext Ref, 155.52 MHz in, 622.08 MHz out

 

0

 

 

 

 

 

 

 

-20

 

 

 

 

 

 

(dBc/Hz)

-40

 

 

 

 

 

 

-60

 

 

 

 

 

 

 

 

 

 

 

 

 

Noise

-80

 

 

 

 

 

 

-100

 

 

 

 

 

 

Phase

 

 

 

 

 

 

-120

 

 

 

 

 

 

 

 

 

 

 

 

 

 

-140

 

 

 

 

 

 

 

-160

 

 

 

 

 

 

 

100

1000

10000

100000

1000000

10000000

100000000

Offset Frequency (Hz)

Dark Blue—37 MHz

Violet—55 MHz

Light Blue—109 MHz

Yellow-Green—163 MHz

Figure 63. Jitter vs. Reference Frequency (1 of 2)

124

Rev. 0.5

Page 124
Image 124
Silicon Laboratories SI5374, SI5369 manual High Reference Frequency, MHz thru 163 MHz Ext Ref, 155.52 MHz in, 622.08 MHz out