Silicon Laboratories SI5375 - Manual (Page 155)

Si53xx-RM
Rev. 1.2 155
A PPENDIX G—N EAR I NTEGER R ATIOS
To provide more details and to provide boundaries with respect to the “Reference vs. Output Frequency” issue
described in Appendix B on page 112, the following study was performed and is presented below.
Test Conditions
 XA/XB External Reference held constant at 38.88 MHz
 Input frequency centered at 155.52 MHz, then scanned.
Scan Ranges and Resolutions:
 ± 50 ppm with 2 ppm steps
 ± 200 ppm with 10 ppm steps
 ± 2000 ppm with 50 ppm steps
 Output frequency always exactly four times the input frequency
 Centered at 622.08 MHz
 Jitter values are RMS, integrated from 800 Hz to 80 MHz
Figure 87. ±50 ppm, 2 ppm Steps
38.88 MHz External XA-XB Reference
0
200
400
600
800
1000
1200
155.51 155.515 155.52 155.525 155.53
Input Frequency (MHz)
RM
S
j
itte
r,
fs
Input Frequency Variation = ±50 ppm