LGE Internal Use Only
Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes
3. TECHNICAL BRIEF
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3.6.2 VCTCXO(X1000: TG-5010LH(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
MSM6285 IC. The oscillator frequency is controlled by the MSM6285 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 warm-up 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 MSM6280 IC require a reference voltage for proper
operation and sufficient accuracy. Connecting the PM6658 IC REF_OUT directly to the MSM6280 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.
3.6.3 FEM(FL1000:D5015)
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],
GPIO[11] and GPIO[12]). These GPIOs are programmed to be ANT_SEL0, ANT_SEL1, ANT_SEL2
and ANT_SEL3 respectively.
Table 1. FEM(Front-End Module) control logic
ANT_SEL0
ANT_SEL1
ANT_SEL2
ANT_SEL3
GSM 850/EGSM TX
HIGH
HIGH
LOW
LOW
PCN/PCS TX
HIGH
LOW
LOW
LOW
WB850
LOW
HIGH
LOW
HIGH
WB1900
LOW
LOW
LOW
HIGH
WB2100
LOW
LOW
HIGH
HIGH
GSM850 RX
LOW
HIGH
HIGH
LOW
EGSM RX
LOW
LOW
HIGH
LOW
PCN RX
LOW
HIGH
LOW
LOW
PCS RX
LOW
LOW
LOW
LOW