LG U8110 Service Manual page 82

3. TECHNICAL BRIEF
B. RFLO Section
The VCO is a fully integrated balanced LC oscillator with on-chip resonator. An on-chip varactor is
used to control the frequency over the desired tuning range.
A separate external voltage regulator supplies the VCO with power to avoid frequency pushing and up
conversion of low frequency noise. A separate ground pin is also used as varactor ground reference to
prevent DC voltage drop changes from affecting the VCO frequency. Via the serial interface, the
VTUNE voltage can be set to VCC/2 to check the center frequency of the VCO. The PLL consists of a
programmable prescaler with multiple division ratios and a phase and frequency detector with a
charge pump with programmable output current. Channel frequency selection is set via the serial
interface.
Figure 3-10. Block diagram of the RFLO section
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