Checking Pam Block - LG U250 Service Manual

4.7.4 Checking PAM Block

TP1. GSM_PA_RAMP : Power Amp Gain Control. typically, 0.2V < Vramp < 1.6V
TP2. GSM_PA_EN : Power Amp Enable
(Power ON : higher than 1.25V , Power OFF : lower than 0.4V)
TP3. GSM_PA_BAND : Power Amp Band Selection Control
(GSM Mode : -0.2V < VBS < 0.4V , DCS/PCS Mode : 1.25V < VBS < 3.0V)
TP4. +VPWR : PAM Supply Voltage Vcc higher than 3.0V
TP1
TP2
4
p
TP3
Rev.D
C123
L403 0.01u
1.5nH
L116
10nH
C134
C438
0.01u
100p
C138 C139
NA 68p
15
DCS_PCS_OUT DCS_PCS_IN
11
EGSM_OUT U101 EGSM_IN
19
RSVD_GND
SKY77318
21
P_GND
TP2
Schematic of GSM PAM Block
- 89 -
4. TROUBLE SHOOTING
TP4
TP4
EGSM
+VPWR
C121
33u
TP1
C136
TP3
0.01u
3
4
R113 100ohm
18
GSM_PA_EN
ENABLE
C149
1
BS 15p
R117 100ohm
GSM_PA_BAND
C153
15p
FL1
EFC