Skyworks Si5338 - Configuring the Input Selection

Si5338-RM
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4. Configuring The Input Selection
The Si5338 is capable of locking to a single-ended clock, a differential clock, or an external crystal resonator
(XTAL). The XTAL allows the Si5338 to generate its own free-running reference clock. A block diagram of the input
configuration of the Si5338 is shown in Figure 6. The Si5338 uses pins IN1/IN2, or IN3 as its main input. Inputs
IN5/IN6, and IN4 can serve as an external feedback path for zero delay mode, or as additional clock inputs if the
device is operating in internal feedback mode.* The following sections describe how each of the inputs are
configured.
*Note: Only Si5338N/P/Q devices allow IN4 to be used as a single-ended clock input.
Figure 6. Si5338 Input Selection Block Diagram
÷P1
IN3
IN2
IN1
Osc
Optional
XTAL
÷P2
IN4
IN6
IN5
p1div_out
p1div_in
PFD
p1div_in
xoclk
pfd_extfb
p2div_in
To VCO
p2div_out
Si5338
Reference Select
Feedback Select
from MSn output
noclk
noclk
fbclk
p2div_in
p2div_out
p1div_in
p1div_out
pfd_in_ref
pfd_in_fb