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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 TxENcontrols receive or transmit mode of the RF switch (Tx= logic 1). Proper timing between transmit enable
TxENand Analog Power Control VRAMP allows for high isolation between the antenna and Tx–VCO while the VCO is
being tuned prior to thetransmit burst. The SKY77550 is compatible with logic levels from 1. V to .9 V for BS, TxEN, and
VSW_EN pads.
Mode
STANDBY
Rx1
1
Rx
Tx_LB
Tx_HB
Rx1 and Rx are broadband receive ports and each supports the GSM850, GSM900, DCS, and PCS bands.
ANT301
C308
1
LGE Internal Use Only
VSW_EN
0
1
1
1
1
Figure 3.3.2 Band SW Logic TableFigure
C302 33p
ANT300
C307
100p
C305
1p
L392
DNI
C316
1n
SW300
L399
GND13
23
2.2n
GND12
24
GND11
25
L313
2.2n
ANT
26
GND10
27
68n
C370
L314
GND9
28
0.5p
PGND
DNI
C321
29
VBAT
Figure 3.3.3 FEM CIRCUIT DIAGRAM
Input Control Bits
TxEN
0
0
0
1
1
L380
12n
C300
2.2p
L302
1n
C303
33n
L381
FILKOR
12n
C306
2.2p
L308
3.3n
C310
1.5p
C311
L310
1n
33p
C312
DNI
3.3n
C317
1.5p
RF_TX_EN
C350
22p
10K
R392
RF_TX_RAMP
C304
2
R391
220p
24K
1
RF_2G_BS
RSVD2
14
R394
RSVD1
13
DNI
U300
BS
12
SMRH0007101
SKY77550
VSW_EN
11
R370
Tx_HB_IN
10
22
RF_HB_TX
Tx_LB_IN
9
C397
GND
33
4.7uF,10V ,M ,X5R ,HD ,1608 ,R/TP
- 3 -
Copyright © 01 LG Electronics. Inc. All right reserved.
3. TECHNICAL BRIEF
BS
0
0
1
0
1
L300
33n
FILKOR
L390
RF_LB_RXP
10n
L391
RF_LB_RXN
10n
L305
33n
FILKOR
L306
5.6n
L350
RF_HB_RXP
3.6n
L311
L351
RF_HB_RXN
3.6n
L312
5.6n
RF_VLOGIC
C301
DNI
RF_LB_TX
Only for training and service purposes
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