Power Amplifier Module - LG GD510 Service Manual

GD510 Operational Description

3.22. Power Amplifier Module

The TQM7M5005H 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 10 PAM pin description
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3. Technical brief
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