Dual Mode Operation - LG KE600 - Cell Phone Service Manual

3. TECHNICAL BRIEF
Table 13 PAM pin description
PIN Function
1 HB_RFIN
2 BAND_SEL Logic low=low band, Logic high=high band select
3 TX_EN
4 VBATT
5 VMODE
6 VRAMP
7 LB_RFIN
8,9,10,11 GND
12 LB_
13,14,15,16,17 GND
18 HB_RFOUT
19,20,21,22,23 GND

3.26. Dual Mode Operation

MODE VMODE
GSM Low
EDGE High
When VMODE is low, the voltage on VRAMP is used to regulate the PA collector voltage which
directly controls the output power. When VMODE is high, the PA collector voltage is regulated to
3.6V, and the supply for the PA base bias can be adjusted via the VRAMP pin to optimize current
drain for low or high power ranges. In addition, in 8PSK mode, the first stage of the low band PA is
bypassed to decrease gain, but in high band, the PA operates with all stages.
3.26.1 PAM Schematic
C640 4.7p
L605 L606
15nH 22nH
L601
3.9nH
C611 C612
0.5p 0.5p
Description
RF input to the High-band PA
PA Enable
Main supply
Logic low=GMSK mode, Logic high=8PSK mode select
Ramped burst pin
RF input to the Low-band PA
Ground
RFOUT RF output from the low-band PA
RF output from the high-band PA
Table 13 PAM pin description
RF INPUT
Fixed
Ramp Burst Control
NC3 LB_RFIN
20 7
NC2 VRAMP
15 6
NC1 VMODE
10 5
VBATT
4
LB_RFOUT TX_EN
12 3
BAND_SEL
2
HB_RFOUT HB_RFIN
18 1
RF3158 U601
VSUPPLY
C620 C621 C613
C638 C639
3p 10p
56p 18p 68u
Figure 42 PAM schematic
- 68 -
VRAMP
Ramp Burst Control
Control amp bias current
LBAND_PAM_IN
R611 15K
HBAND_PAM_IN
R612 R613
100K 100K
TX ENABLE
High
High
PA_LEVEL
MODE
TXON_PA
PA_BAND
R614
100K