11. Internal Reference
Devices with internal reference (J/K/L/M) have a 48MHz crystal integrated in the package, to deliver a smaller layout footprint and more
immunity to acoustic emissions. This crystal is manufactured by a reliable Japanese crystal manufacturer and has been pre-screened
for activity dips before being assembled. It is important to note that connecting an external reference to XA/XB of a device that already
has an integrated reference is not allowed. Doing so could lead to internal damage to the circuits. When using this integrated crystal
option in a design that has been laid out for an external crystal, simply depopulate the crystal and replace the external crystal device
with the internal crystal version. It is important to note that a new CBPro plan is required for the integrated crystal variant. For more
information, please contact Silicon Labs support. For specifications of the internal crystal, please refer to the data sheet. During the
initial power up, the integrated crystal quickly settles down to a temperature that is slightly higher than ambient temperature due to prox-
imity to the die. If the PLL is locked to an input, the frequency accuracy of the crystal has no impact on the output frequency accuracy; if
the PLL is free-running, then the output frequency tracks the crystal frequency which is still well within the spec.
Si5397/96 Reference Manual
Internal Reference
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