S i 5 3 4 5 - E V B
Rev. 1.1
5
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
Si5345-EVB can also accommodate an external reference clock instead of a crystal. To evaluate the device with a
REFCLK, C111 and C113 must be populated and the XTAL removed (see Figure 4 below). The REFCLK can then
be supplied to J39 and J40.
Figure 4. External Reference Input Circuit
