LG GB220 - FEM with Integrated Power Amplifi er Module; (Sky77531, U400)

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Copyright © 2009 LG Electronics. Inc. All right reserved.
Only for training and service purposes
LGE Internal Use Only
3. TECHNICAL BRIEF
Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes
LGE Internal Use Only
3.3.1 Internal Block Diagram
3.3 FEM with integrated Power Amplifier Module (SKY77531, U400)
Figure. 3-3-1 SKY77531 FUNCTIONAL BLOCK DIAGRAM
3.3.2 General Description
The SKY77531 is a transmit and receive front-end module (FEM) with Integrated Power Amplifier Control for
quad-band cellular handsets comprising GSM850/900 and DCS1800/PCS1900 operation. Designed in a low
profile, compact form factor.
The FEM also supports Class 12 General Packet Radio Service (GPRS) multi-slot operation.
The module consists of a GSM850/900 PA block and a DCS1800/PCS1900 PA block, impedance matching
circuitry for 50 Ω input and output impedances, TX harmonics filtering, high linearity and a low insertion
loss PHEMT RF switch, and a Power Amplifier Control (PAC) block with internal current sense resistor. A
custom BiCMOS integrated circuit provides the internal PAC function and decoder circuitry to control the RF
switches. The two Heterojunction Bipolar Transistor (HBT) PA blocks are fabricated onto a single Gallium
Arsenide (GaAs) die. One PA block supports the GSM850/900 bands and the other PA block supports the
DCS1800/PCS1900 bands. Both PA blocks share common power supply pads to distribute current. The
output of each PA block and the