Service Manual
149
rge pump is 5V. See the following figure:
divider, phase detector, charge pump and etc. The voltage of analog circuit and digital circuit of PLL IC is
3.3V voltage, while the voltage of cha
Figure 10-6 Block Diagram of PLL IC
SKY72310’s role is to generate appropriate frequency based on the data transmitted by OMAP of
baseband board. The 19.2MHz frequency generated by the reference crystal oscillator goes into the PLL,
to generate the reference frequency. Meanwhile, the frequency generated by VCO goes into PLL for
frequency division. The resulting frequency will be compared with reference frequency in terms of phase
difference in the phase detector. After comparison, the resulting frequency is converted to CV voltage via
the loop filter, to control the output frequency of VCO. In addition, as a key component of the modulation
circuit, PLL can directly obtain d ulation.
(Q101 and Q107), a varactor and four Colpitts
rs. Q105 and Q106 are the buffer amplifiers for the exciter unit.
ata from the MCSI port of OMAP for mod
VCO
The VCO for RX unit comprises two transistors (Q101 and Q107), a varactor and four Colpitts oscillators.
Q105 and Q106 are the buffer amplifiers for the RX unit.
The VCO for exciter unit comprises two transistors
oscillato
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