3. TECHNICAL BRIEF
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Copyright © 011 LG Electronics. Inc. All right reserved.
Only for training and service purposes
LGE Internal Use Only
Figure 3.3.2 Band SW Logic Table
Figure 3.3.3 FEM CIRCUIT DIAGRAM
Band selection and control of transmit and receive are performed using four external control pads. Refer to the
block diagram in Figure 1 below. The band select pad, BS, selects GSM850, GSM900, DCS, and PCS modes of
operation. Transmit enable TxEN controls receive or transmit mode of the RF switch (Tx = logic 1). Proper
timing between transmit enable TxEN and Analog Power Control VRAMP allows for high isolation between the
antenna and Tx–VCO while the VCO is being tuned prior to the
transmit burst. The SKY77550 is compatible with logic levels from 1.2 V to 2.9 V for BS, TxEN, and VSW_EN pads.
100
R304
L304
1n
L309
18n
C345
4.7p
C313
1p
DNI
C312
C346
4.7p
C331
100p
L308
1n
C344
4.7p
C318
33p
C302 22p
C317
2.2n
R316
DNI
R315
75
DNI
C347
L305
15n
L316
9p
3n
L301
SW301
2
G
T
N
A
F
R
1
G
C321
3.9p
C319
DNI
C343
100n
DNI
L313
C316
1p
VBAT
9p
L315
DNI
L314
C310
2.2p
9p
C304
4.7u
C323
4.7u
C329
9p
C301
942.5 MHz,35 MHz
FL301
10
5
3
2
6
4
7
8
9
1 I1
O1_1
O1_2
O2_1
I2
O2_2
1
G
2
G
3
G
4
G
ANT301
C315 10p
ANT304
C322
4.7p
U301
29
23
24
25
26
27
28
5
1
6
1
7
1
8
1
9
1
0
2
1
2
2
2
8
7
6
5
4
3
2
1
14
13
12
11
10
9
Tx_LB_IN
Tx_HB_IN
VSW_EN
BS
RSVD1
RSVD2
1
D
N
G
2
D
N
G
1
T
T
A
B
V
2
T
T
A
B
V
3
D
N
G
4
D
N
G
5
D
N
G
6
D
N
G
7
D
N
G
2
x
R
3
D
V
S
R
1
x
R
D
V
S
R
N
E
x
T
P
M
A
R
V
8
D
N
G
GND9
GND10
ANT
GND11
GND12
GND13
PGND
RF_TX_RAMP
RF_TX_EN
RF_LB_TX
RF_HB_RXN
RF_HB_RXP
RF_LB_RXN
RF_LB_RXP
GND
RF_HB_TX
RF_VLOGIC
RF_2G_BS
(10V,1608)
TX module