Front End Module Control - LG Prada KE850 Service Manual

3. TECHNICAL BRIEF

3.26. Front End Module control

Implemented in the S-Gold2 (U101) are three outputs which are VC2, VC3 and VC4 for direct control
of front end modules with three logic input pins to select RX and TX mode as well as low and high
band operation.
Table 12 FEM Control Logic
MODE Tx 1GHz
VDD ON
VCTRL1 ON
VCTRL2 OFF
VCTRL3 OFF
Front End Module
GSM850
EGSM
DCS
PCS
LB RF Input
HB RF Input
C416 C417 C418
1.5p 1.5p 1.2p
L406 L407
Tx 2GHz
ON
ON
ON
OFF
VRF2V85
U401
YGHF-S006A
18 3
GMS_RX- VDD
19 22
GSM_RX+ VCTRL1
16 21
EGSM_RX- VCTRL2
17 20
EGSM_RX+ VCTRL3
14
DCS_RX-
15 2
DCS_RX+ GND1
12 4
PCS_RX- GND2
13 5
PCS_RX+ GND3
7
GND4
6 9
TX1G GND5
8 10
TX2G GND6
C419
1.2p
Figure 40 FEM schematic
Rx GSM Rx EGSM
ON ON
OFF OFF
ON ON
ON OFF
R403
0
C405
0.1u
C464 C465
C467
100p 100p
100p
- 68 -
Rx DCS TX PCS
ON
OFF
OFF
ON
R435 100
R436 100
R437 100
R438 0
C466
NA
ON
OFF
OFF
OFF
VC4
VC3
VC2
VC1