LG U300 Service Manual page 90

4.6.4 Checking PAM Block
PAM Control Signal
TP1. GSM_PA_RAMP : Power Amp Gain Control. typically, 0.5V < Vapc < 2.6V,
TP2. GSM_PA_EN : Power Amp Enable
(Power ON : higher than 2.5V , Power OFF : lower than 0.7V)
TP3. GSM_PA_BAND : Power Amp Band Selection Control
(GSM Mode : lower than 0.7V , DCS/PCS Mode : higher than 2.5V)
TP4. +VPWR : PAM Supply Voltage Vcc higher than 3.28V
TP2
C123
1p
C139
3.3p
Test Point (RF Tx Level)
9 1
DCS_PCS_OUT DCS_PCS_IN
2
BAND_SELECT
26
GND17
27 3
GND18 TX_ENABLE
28 U102
GND19
29 4
GND20 VBATT
SMPY0008901
30
GND21
31 5
GND22 GND
32
GND23 RF3166
6
VRAMP
8 7
GSM_OUT GSM_IN
Schematic of PAM block
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4. TROUBLE SHOOTING
R105 100
GSM_PA_BAND
C113
15p
R108 100
GSM_PA_EN
C117
15p
R110
24
R115
200
R116
150
+VPWR
C132 C605
22u 0.01u R118
220
R121
15
R123
270
R125
GSM_PA_RAMP
0
TP3
TP4
TP1