Power Amplifier Module - LG KP500 Service Manual

3.23 Power Amplifier Module

The SKY77340 Power Amplifier Module(PAM) is designed in a compact from fact for quad-band
cellular handsets comprising GSM850/900,DCS1800,PCS1900,supporting GMSK and linear EDGE
modulation.
Class12 General Packet Radio Service(GPRS) multi-slot operation is also supported.
The module consists of a GSM850/900 PA block and a DCS1800/PCS1900 PA block,impedance
matching circuitry for 50ohm input and output impedances, and a Multi-function Power Amplifier
Control(MFC) block. A custom CMOS integrated circuit provides the internal MFC function and
interface circuitry.
Two separate Heterojunction Bipolar Transistor(HBT) PA blocks are fabricated onto InGaP die; one
supports the GSM850/900 bands, the other supports the DCS1800 and PCS1900 bands. Both PA
blocks share common power supply pins to distribute current. The InGaP die, the silicon die, nad the
passive components are mounted on a multi layer laminate substrate. The assembly is encapsulated
with plastic overmold.
RF input and output ports are internally matched to 50ohm to reduce the number of external
components Extremely low leakage current(2.5uA) maximizes handset standby time. Band select(BS)
circuitry select GSM transmit frequency band(logic0) and DCS/PCS transmit frequency(logic1). MODE
circuitry selects GMSK modulation (logic0) or EDGE modulation(logic1). VRAMP controls the output
power for GMSK modulation and provides bias optimization for EDGE modulation depending on the
state of MODE control.
The integrated multi-function(MFC) provides envelope amplitude control in GMSK mode, reducing
sensitivity to input drive, temp, power supply, and process variation. In EDGE mode, the MFC
configures the PA for fixed gain, and provides the ability to optimize the PA bias operation at different
power levels, This circuitry regulates PA bias conditions, reducing sensitivity to temp., power supply,
and process variation. The Enable input signal(pin8) provides a standby state to minimize battery
drain.
Table 13 PAM pin description
Pin Mame
1 MODE
2 DCS/PCS_IN
3 BS
4 VBIAS
5 VBATT
6 VRAMP
7 GSM_IN
8 EN
9 GSM_OUT
*12 REVD2
*10,11,13-15 GND
*16 DCS/PCS_OUT
Pad GND PAD GRID
Copyright © 2008 LG Electronics. Inc. All right reserved.
Only for training and service purposes
GMSK/EDGE Power control mode. L=GMSK, H=EDGE
RF input(DCS/PCS) DC Blocked
Band Select
Analog PA Bias Control(All Bands, EDGE Mode)
DC Supply
Analog Output Power Control(All Bands, GMSK Mode)
RF input(CEL/EGSM) DC Blocked
Transmit Enable/Disable. Low=Disable
RF Output(CEL/EGSM) DC Blocked
Reserved
Ground
RF Output(DCS/PCS) DC Blocked
Ground pad grid is device underside.
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3. TECHNICAL BRIEF
Description
LGE Internal Use Only