SI5344-EVB Datasheet, PDF (5/19 Pages) Silicon Laboratories – Powered from USB port or external power supply

Si5344-EVB
6. External Reference Input (XA/XB)
An external reference (XTAL) is used in combination with the internal oscillator to produce an ultra-low jitter
reference clock for the DSPLL and for providing a stable reference for the free-run and holdover modes. The
Si5344-EVB can also accommodate an external reference clock instead of a crystal. To evaluate the device with a
REFCLK, C93 and C94 must be populated and the XTAL removed (see Figure 3). The REFCLK can then be
applied to J25 and J26.
Figure 3. External Reference Input Circuit
7. Clock Input Circuits (INx/INxB and FB-IN/FB-INB)
The Si5344-EVB has eight SMA connectors (IIN0/IN0B – IN2/IN2B and IN3(FB_IN)/IN3B(FB_INB)) for receiving
external clock signals. All input clocks are terminated as shown in Figure 4.
Input clocks are AC coupled and 50- terminated. This represents 4 differential input clock pairs. Single-ended
clocks can be used by appropriately driving one side of the differential pair with a single-ended clock. For details on
how to configure inputs as single-ended, please refer to the Si5344 data sheet.
Figure 4. Input Clock Termination Circuit
Rev. 1.0
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