Power Amplifier Module (Pam : Sky77340, U502) - LG KE800 Service Manual

3. TECHNICAL BRIEF
(5) Front End module control
Implemented in the SMARTiPM are two outputs for direct control of front end modules with two logic input
pins to select RX- and TX-mode as well as low- and highband operation.

3.2 Power Amplifier Module (PAM : SKY77340, U502)

The SKY77340 Power Amplifier Module (PAM) is designed in a compact form factor for quad-band cellular
handsets comprising GSM850/900, DCS1800, PCS1900, supporting GMSK and linear EDGE modulation.
Class 12 General Packet Radio Service (GPRS) multi-slot operation is also supported. (Class 10 is used in
KE800)
The module consists of a GSM850/900 PA block and a DCS1800/PCS1900 PA block, impedance matching
circuitry for 50Ω 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. RF input and
output ports are internally matched to 50Ω to reduce the number of external components. Extremely low
leakage current (2.5uA, typical) maximizes handset standby time. Band select (BS) circuitry selects GSM
transmit frequency band (logic 0) and DCS/PCS transmit frequency band (logic 1). MODE circuitry selects
GMSK modulation (logic 0) or EDGE modulation (logic 1). VRAMP controls the out power for GMSK
modulation and provides bias optimization for EDGE modulation depending on the state of MODE control.
The integrated multi-function control (MFC) provides envelope amplitude control in GMSK mode, reducing
sensitivity to input drive, temperature, 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 temperature, minimize battery
drain.
Figure. 3-4 SKY77340 Functional Block Diagram
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