6. External Reference Input (XA/XB)
An external timing reference (48 MHz 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 Si5397-A-EB can also accommodate
an external reference clock instead of a crystal.To evaluate the device with an external REFCLK, C111 and C113 must be populated
and XTAL Y1 removed (see figure below). The REFCLK can then be applied to SMA connectors J39 and J40.
Figure 6.1. External Reference Input Circuit
UG353: Si5397 Evaluation Board User's Guide
External Reference Input (XA/XB)
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