SI5317-EVB Datasheet, PDF (3/20 Pages) Murata Manufacturing Co., Ltd. – Si5317 EVALUATION BOARD

Si5317-EVB
2. Si5317-EVB Input and Output Clocks
2.1. Input Clocks
The Si5317-EVB has a differential clock input that is ac terminated and ac coupled before being presented to the
Si5317. If the input clock frequencies are low (below 10 MHz), there are extra considerations that should be taken
into account. The Si5317 has a maximum clock input rise time specification of 11 ns that must be met (see CKNtrf
in the Si5317 data sheet). Also, if the input clock is LVCMOS, it might be advantageous to replace the input
coupling capacitors (C7, C12, C16. and C18) with 0  resistors. When using LVCMOS inputs, the user should
consider removing the ac termination and using source series termination located at the driving source.
Regardless of the input format, if the clock inputs are not approximately 50% duty cycle, it is highly recommended
to avoid ac coupling. For input clocks that are far off of 50% duty cycle, the average value of the signal that passes
through the coupling capacitor will be significantly off of the midpoint between the maximum and minimum value of
the clock signal, resulting in a mismatch with the common mode input threshold voltage (see Vicm, in the Si5317
data sheet).
2.2. XA-XB Reference
To achieve a very low jitter generation and for stability during holdover, the Si5317 requires a stable, low jitter
reference at its XA-XB pins. To that end, the EVB is configured with a 114.285 MHz third overtone crystal
connected between pins 6 and 7 of the Si5317. However, the Si5317-EVB is also capable of using an external XA-
XB reference oscillator, either differential or single-ended. For details concerning the allowed XA-XB reference
frequencies and their RATE settings, see the Si5317 data sheet. J1 and J2 are the SMA connectors with ac
termination. AC coupling is also provided that needs to be installed at C6 and C8. Table 1 explains the component
changes that are needed to implement an external XA-XB reference oscillator.
Table 1. XA-XB Reference Connections
Ext Ref In+
Ext Ref In-
C6, C8
R8
RATE0^{(See note 4)}
RATE1^{(See note 4)}
Notes:
1. Xtal is 114.285 MHz.
2. NC - no connect.
3. NOPOP - do not install.
4. J12 jumper, see Table 3.
5. C6 on bottom of the board.
Mode
Xtal
NC
NC
NOPOP
install
M
M
Ext Ref
J1
J2
install
NOPOP
H
M
Rev. 0.1
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