LG L705ix Service Manual page 20

3.3.1 UMTS Rx PLL (PLL2)
QUALCOMM provides a baseline PLL2 design for UMTS Rx. Loop filter component reference
designators are shown in Figure 3.3-1.
Notes: 1. The performance values listed in this table are based on simulation results and are provided
as a starting point for handset designers. Synthesizer performance is stillbeing evaluated
and optimized during this document release. Loop parameter, settling time, and filter
component values are all expected to change when the optimization effort is completed.
Future revisions will include expected performance based on measured data.
2. For L705iX, C1_2.2nF C2_150pF R1_10k
3. Loop parameter acronyms are: Kvco VCO tuning sensitivity CP_I Charge pump current
(controlled by API software) PM Phase margin L_BW Loop bandwidth
4. The listed VCO tuning sensitivity is based on QUALCOMM internal Rx VCO.
5. The listed settling times are for switching between channels at opposite ends of the active
band and settling to within 250 Hz of the final frequency.
6. Test and evaluation efforts were ongoing at the time of this document release.
Check future versions for design recommendations based on our test results.
3.3.2 Transceiver PLL (PLL1)
The PLL1 within the RTR6275 IC creates the Rx LO for all the GSM receive bands and GSM transmit
bands as well as the UMTS transmit bands. The PLL1 of RTR6275 IC (with on-chip VCO) creates the
transceiver LO that supports the quad-band GSM receivers and the GSM transmitters as well as the
tri-band UMTS transmit outputs. All LO functional blocks are integrated into the RTR6275 IC except for
some loop filter capacitors (Figure 3.3-1). On- chip circuits include reference divider, phase detector,
charge pump, VCO, feedback divider, and digital logic status.
The off-chip loop filter capacitors allow minimal optimization of PLL performance characteristics
(stability, transitory response, settling time, and phase noise) for different applications.
Copyright © 2008 LG Electronics. Inc. All right reserved.
Only for training and service purposes
Table 3.3-1 Baseline PLL2 design for UMTS Rx
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3. TECHNICAL BRIEF
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