Power Amplifier Module - LG GS290 Service Manual

3. TECHNICAL BRIEF
GS290 Operational Description

3.21. Power Amplifier Module

The SKY77344 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..
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Table 9 PAM pin description
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