LG CU920 Manual page 101

4.8.2 Checking PAM Block
1. TP1 : GSM_PA_RAMP
→ Power Amp Gain Control. typically, 0.2V < Vramp < 1.6V
2. TP2 : GSM_PA_EN
→ Power Amp Enable (Power ON : higher than 1.25V, Power OFF : lower than 0.4V)
3. TP3 : GSM_PA_BAND
→ Power Amp Band Selection Control
(GSM Mode : -0.2V < VBS < 0.4V, DCS/PCS Mode : 1.25V < VBS < 3.0V)
4. TP4 : +VPWR
→ PAM Supply Voltage Vcc higher than 3.0V
5. TP5 : GSM_SAW_SW_MODE
→ High : G900, Low : G850
16
DCS_PCS_OUT U101
SKY77329
9
GSM_OUT
Copyright © 2008 LG Electronics. Inc. All right reserved.
Only for training and service purposes
TP2
TP3
TP4
TP1
TP5
Fig. 4.8.2.1 Test point of the GSM PAM Block
TP1
GSM_PA_RAMP
R113 2.2K
C128
68p
C132 C129
33p 33u
R116
82
2
DCS_PCS_IN
7
GSM_IN
1
TX_EN GSM_PA_EN
3
BS GSM_PA_BAND
TP2
TP3
Fig. 4.8.2.2 Schematic of the GSM PAM Block
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4. TROUBLE SHOOTING
TP4
+VPWR
R115
82
DCS_PCS_TX
R117
82
FL101
LMSM32AA-533
5 1
RFOUT RFIN
7
VC
R122
200
C143
NA
R119
51
GSM_TX
7.75dB
R120 R121
110 110
GSM_SAW_SW_MODE
EGSM LOW
GSM850 HIGH
remain LOW when not transmitting
TP5
LGE Internal Use Only