Off-Chip Rf Components - LG KF700 Service Manual

3. TECHNICAL BRIEF

3.5 Off-chip RF Components

3.5.1 UMTS PAM (U105: AWT6279R)
The UMTS PA output power is monitored by power detector circuits (U100 : RTR6275) .
This detector voltage can be used for transmitter calibration and monitor to meet RF system
specification.
FL103
SAYZY1G95EA0B00
+VPWR
C170
22p
U104
SCDY0003801
L120
1.8nH
1 2
L122
C173
4.7nH
DNI
20dB
R116
R117
47 47
R118 R119
8 dB
120 100ohm
3.5.2 VCTCXO (X100 :DSA321SCE-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 MSM6280 IC. The
oscillator frequency is controlled by the MSM6280 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 PM6650 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 PM6650 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 PM6650 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.
LGE Internal Use Only
C160
C162
4.7u
0.01u
smd_1608h_9_r
U105
AWT6279R
11
PGND
10 1
VCC VBATT
9 2
C171
GND3 RFIN
8 3
RFOUT VMODE2
7 4
GND2 VMODE1
2.2p
6 5
GND1 VEN
C174
DNI
PWR_DET
[Fig. 3.5] UMTS PAM, Duplexer, Coupler
L118
EFCH1950TDF1
1nH
C164
C163
0.01u C539
4.7u C165
DNI 1p
smd_1608h_9_r
PA_R1
PA_ON
C175 C176
0.01u
100p
Copyright © 2008 LG Electronics. Inc. All right reserved.
- 22 -
FL104
4 5
C161 56p
O1 G3
1
WCDMA_2100_TX_OUT
IN
G2 G1
3 2
L119
3.9nH
Only for training and service purposes