SI5340-EVB Datasheet, PDF (5/19 Pages) Silicon Laboratories – Powered from USB port or external power supply

Si5340-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
Si5340-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 below). 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 Si5340-EVB has eight SMA connectors (IN0/IN0B – IN2/IN2B and FB_IN/FB_INB) for receiving external clock
signals. All input clocks are terminated as shown in Figure 4 below.
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 Si5340 data sheet.
Figure 4. Input Clock Termination Circuit
Rev. 1.0
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