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Si53xx-RM
162 Rev. 0.5
APPENDIX G—NEAR INTEGER RATIOS
To provide more details and to provide boundaries with respect to the “Reference vs. Output Frequency” issue
described in Appendix B on page 121, 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 85. ±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)
RMS jitter, fs
Input Frequency Variation = ±50 ppm