Lo Phase-Locked Loop; Only For Training And Service Purposes - LG KP330 Service Manual

3. TECHNICAL BRIEF

3.5 LO Phase-locked Loop

All LO functions are fully integrated on-chip and do not require any user adjustment.
Qualcomm has established and implemented frequency plans and LO generation schemes
that support the radioOne Platform F/G-series chipset. Only one area requires handset
designer attention: the loop filters relating to each PLL. These are addressed in this chapter.
All the UMTS Tx/Rx, GSM Tx/Rx and GPS PLL circuits are included within the RTR6285:
reference dividers, phase detectors, charge pumps, feedback dividers, and digital logic. The
RTR6280 integrates all the same PLL circuits as the RTR6285 with the exception of GPS.
There are three integrated VCOs and PLLs within the Platform F/G (RFCMOS) chipset as
shown in Figure 1.5-1:
PLL1 produces the LO for up-/down-conversion of GSM Tx/Rx, and UMTS Tx
■
PLL2 produces the Rx LO for the UMTS primary and diversity down-conversion
■
PLL3 produces the LO for GPS down-conversion
■
A buffered 19.2 MHz VCTCXO signal provides the synthesizer input (VCTCXO), the frequency
reference to which the PLL is phase- and frequency-locked. The reference is divided by the
Rcounters to create a fixed-frequency input to the phase detector, F
detector input (F ) varies as the loop acquires lock, and is generated by dividing the VCO
V
frequency using the feedback path N-counter. The closed loop will force F
locked. If the loop is not locked, the error between F
output of the charge pump. This error signal is filtered by the loop filter components and
applied to the VCO, tuning the output frequency so that the error is decreased. Ultimately, the
loop forces the error to approach zero and the PLL is phase- and frequency-locked. All of the
key PLL components affecting the PLL performance – such as VCO sensitivity, charge pump
circuit current, PLL topology and loop filter (with the exception of one capacitor) – are
integrated into the RFIC. This means that proper handset performance is assured.
LGE Internal Use Only
KP330 Operational Description
and F will create an error signal at the
V R
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. The other phase
R
to equal F when
V R

Only for training and service purposes