MC12439
Description
The internal oscillator uses the external quartz crystal as the basis of its frequency reference. The output of the reference oscillator is sent directly to the phase detector. With a 16.66MHz crystal, this provides a reference frequency of 16.66MHz. Although this data sheet illustrates functionality only for a 16MHz and 16.66MHz crystal, any crystal in the 10- 20MHz range can be used. In addition to the crystal, an LVCMOS input can also be used as the PLL reference. The reference is selected via the XTAL_SEL input pin. The VCO within the PLL operates over a range of 400 to 800MHz. Its output is scaled by a divider that is configured by either the serial or parallel interfaces. The output of this loop divider is also applied to the phase detector. The phase detector and loop filter attempt to force the VCO output frequency to be M times the reference frequency by adjusting the VCO control voltage. Note that for some values of M (either too high or too low) the PLL will not...
