NA
L503
1
R511
1
R514
3
BS
BY_CAP1
13
9
BY_CAP2
DCS_PCS_IN
1
12
DCS_PCS_OUT
GND1
14
11
GND2
8
GND3
GSM850_900_IN
7
GSM850_900_OUT
10
MODE_SELECT
2
PGND
15
6
TX_EN
VBATT
4
VRAMP
5
TQM7M5005
U501
VBAT
100p
C523
DNI
L504
100p
C507
R516
4.7nH
1
R509
1
R513
27p
C521
1000p
C520
R512
1.2K
22u
C506
C524
820p
C522
100p
TXLB
TXHB
PA_EN
PA_MODE
TX_RAMP
PA_BAND
- 103 -
Copyright © 2008 LG Electronics. Inc. All right reserved.
Only for training and service purposes
LGE Internal Use Only
5. TROUBLE SHOOTING
5.14.1 Transmitter Circuit
Fig 13 Transmitter circuit (U104)
9
Check point of PAM
- Transmitter output power (=R505, L572) is approximately 3dBm.
5.14.2 PAM Circuit
9
PAM
circuit
contains
as
below
- Band select switching circuitry (BS) to select GSM (Logic 0) and DCS/PCS (Logic1).
- VRAMP controls the level of output power for GMSK modulation and shape of Tx burst.
- For GMSK operation, set the PA_EN input High, and PA_MODE low(0.5v)
Operational status
PA_EN
PA_BAND
PA_MODE
TX_RAMP
Standby/PA off
0
X
X
X
Low Band GMSK Tx
1
0
0
Active
Low Band EDGE Tx
1
0
1
X
TP1
Does Power
(TP1 & TP2)
seem like
about 3dBm?
Check
U102
Check the next part
YES
NO
Transmitter Circuit
TP2
TP2
TP1