LG U250 Service Manual page 29

3. TECHNICAL BRIEF
3.5.5 GSM PAM (U101 : SKY77318)
The SKY77318 is an extremely small (6 x 6 mm), GSM PAM for handset applications. This module
has been optimized for excellent efficiency and Pout while maintaining high GSM/GPRS efficiency.
The small size and high performance is achieved with high-reliability GaAs HBT technology.
With 50Ω and output, no external matching or bias components are required. The module incorporates
two highly-integrated GaAs power amplifier die with a BiCMOS controller.
Each amplifier has three gain stages with on-die inter-stage matching implemented with a high Q
passives technology for optimal performance. The CMOS controller implements a fully integrated
power control within the module for GSM operations, and serves as the GPRS operations. This
eliminates the need for any external couplers, power detectors, current sensing etc., to assure the
output power level. The module has Tx enable and band select inputs. Module construction is a low-
profile overmolded land-grid array on laminate.
Rev.D
C124 L403
100p 1.5nH
L116
L115
10nH
18nH
C441 C438
5.6p 100p
C137 C138
NA NA
15
11
19
21
+VPWR
C123 C121
33u
0.01u
C134
0.01u
C136
C139 0.01u
68p
3
DCS_PCS_OUT DCS_PCS_IN
4
EGSM_OUT U101 EGSM_IN
18
RSVD_GND ENABLE
SKY77318
1
P_GND BS
R117
C153
15p
[Figure 1. 8] GSM PAM Schematic
EGSM
NA
L406
FL101
4 5
O1 G3
G2 G1
R113 100ohm
3 2
GSM_PA_EN
C149
15p
EFCH897MTDB1
100ohm
GSM_PA_BAND
GSM_PA_BAND
- 30 -
L111
5.6nH
2.7nH
8.86dB Rev.1.0
R108
51
7.5dB
R112
1
GSM_TX
IN
39
MODE
LOW GSM
DCS/PCS
HIGH
DCS_PCS_TX