SI5317 Datasheet, PDF (30/50 Pages) Silicon Laboratories – Pin-Controlled 1_710 MHz Jitter Cleaning Clock

Si5317
5. Crystal/Reference Clock Input
The device can use an external crystal or external clock as a reference. If an external clock is used, it must be ac
coupled. With appropriate buffers, the same external reference clock can be applied to CKIN. Although the
reference clock input can be driven single ended (See Figure 15), the best performance is with a crystal or
differential clock source.
3.3 V
3.3 V
130 
CMOS buffer,
8 mA output current
150 
0.1 F
XA
XB
150 
Si5317
10 k
0.6 V
0.1 F
For 2.5 V operation, change 130  to 82 .
Figure 15. CMOS External Reference Circuit
0 dBm into 50 
External Clock Source
0.01 F _XA
Si5317
1.2 V
0.01 F
10 pF
XB
10 k
50 
0.1 µF
0.6 V
Figure 16. Sinewave External Reference Clock Input Example
LVPECL, CML, etc.
100 
0.01 F _XA
Si5317
1.2 V
XB
0.01 F
10 k
10 k
0.6 V
Figure 17. Differential External Reference Clock Input Example
30
Preliminary Rev. 0.15