LG HB620 Service Manual page 31

3. TECHNICAL BRIEF
3.5.5 GSM PAM (U102 : SKY77329)
The SKY77329 Power Amplifier Module (PAM) is designed in a compact form factor for quad-band
cellular handsets comprising GSM850/900, DCS1800, PCS1900, and supports Class 12 General
Packet Radio Service (GPRS) multi-slot operation.
The module consists of a GSM850/900 PA block and a DCS1800/PCS1900 PA block, impedance
matching circuitry for 50 Ω input and output impedances, and a Power Amplifier Control (PAC) block.
A custom CMOS integrated circuit provides the internal PAC function and interface circuitry. Two
separate Hetero-junction Bipolar Transistor (HBT) PA blocks are fabricated onto InGaP/GaAs die; one
supports the GSM850/900 bands, the other supports the DCS1800 and PCS1900 bands. Both PA
blocks share common power supply pins to distribute current. The GaAs die, the silicon die, and the
passive components are mounted on a multi-layer laminate substrate and the entire assembly is
encapsulated with plastic overmold.
R107
GSM_PA_RAMP
2.2K
C136
56p
C137 16
DCS_PCS_OUT
NA
9
GSM_OUT
C138
56p
C141
NA
LGE Internal Use Only
+VPWR
C126 C127
33u
1u
C132
68p
2
DCS_PCS_IN
7
U102 GSM_IN
SKY77329
1
TX_EN
3
BS
C139 C140
15p 15p
[Fig. 3.7] GSM PAM Schematic
- 32 -
R108
DCS_PCS_TX
68
R109 R110
91 91
4 5
GSM_PA_EN
FL102 O1 G3
1
GSM_PA_BAND
IN
G2 G1
EFCH897MTDB1
3 2
Copyright © 2008 LG Electronics. Inc. All right reserved.
Only for training and service purposes
R112
GSM_TX
51
R114 R115
120 120