LG KF310 Service Manual page 20

3.5.2 VCTCXO (X1000 :DAS321SCE-19.2M)
The Voltage Controlled Temperature Compensated Crystal Oscillator (VCTCXO) provides the
reference frequency for all RFIC synthesizers as well as clock generation functions within the
MSM6245 IC. The oscillator frequency is controlled by the MSM6245 ICs. TRK_LO_ADJ pulse density
modulated signal in the same manner as the transmit gain control TX_AGC_ADJ. A two-pole RC
lowpass filter is recommended on this control line. The PM6658 IC controls the handset power-up
sequence, including a special VCTCXO warmup interval before other circuits are turned on. This
warm-up interval (as well as other TCXO controller functions) is enabled by the MSM TCXO_EN line .
The PM6658 IC VREG_TCXO regulated output voltage is used to power the VCTCXO and is enabled
before most other regulated outputs.
Any GSM mode power control circuits within the MSM6245 IC require a reference voltage for proper
operation and sufficient accuracy. Connecting the PM6658 IC REF_OUT directly to the MSM6275 IC
GSM_PA_PWR_CTL_REF provides this reference. This sensitive analog signal needs a 0.1 µF low
frequency filter near to MSM side, and isolate from digital logic and clock traces with ground on both
sides, plus ground above and below if routed on internal layers.
3.5.3 Front-End Module (FL1000 : DGM129M01)
This equipment uses a single antenna to support all handset operating modes, with an antenna switch
module select the operating frequency and band. UMTS operation requires simultaneous reception
and transmission, so the UMTS Rx/Tx connection is routed to a duplexer that separates receive and
transmit signals. The active connection is MSM-selected by three control lines (GPIO[9], GPIO[10],
and GPIO[11]). These GPIOs are programmed to be ANT_SEL0, ANT_SEL1, and ANT_SEL2
respectively.
GSM850/EGSM TX
PCN/PCS TX
WB2100
EGSM RX
PCN RX
PCS RX
Copyright © 2008 LG Electronics. Inc. All right reserved.
Only for training and service purposes
ANT_SEL0
HIGH
HIGH
HIGH
LOW
LOW
LOW
[Table 3.5.3.1] Front End Module control logic
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3. TECHNICAL BRIEF
ANT_SEL1 ANT_SEL2
LOW
HIGH
LOW
HIGH
LOW
HIGH
LGE Internal Use Only
HIGH
LOW
LOW
LOW
HIGH
LOW