Fem With Integrated Power Amplifier Module - LG -A290 Service Manual

3.3 FEM with integrated Power Amplifier Module (SKY77550, U400)
3.3.1 Internal Block Diagram
TX_HB_IN(10)
VBATT (3)
VBATT (4)
VRAMP (16)
TxEN (18)
BS (1)
VSW_EN (11)
Tx_LB_IN (9)
3.3.2 General Description
SKY77550 is a transmit and receive Front-End Module (FEM) with Integrated Power Amplifier Control(iPAC™) for Dual-
band cellular handsets comprising GSM850/900 and DCS1800/PCS1900 operation. Designed in a low profile, compact
form factor, the SKY77550 offers a complete Transmit VCO-to-Antenna and Antenna-to-Receive SAW filter solution. The
FEM also supports Class 1 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 ohm input and output impedances, Tx harmonics filtering, high linearity / low insertion loss RF switch, and a Power
Amplifier Control (PAC) block with internal current sense resistor. The two Hetero-junction Bipolar Transistor (HBT) PA
blocks, a Bi-FET PAC and switch control circuit 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.
LGE Internal Use Only
HBT POWER AMPLIFIER
CURRENT SENSE
POWER AMPLIFIER CONTROL
LOGIC DECODER
Figure. 3.3.1 SKY77550 FUNCTIONAL BLOCK DIAGRAM
Match
Match
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3. TECHNICAL BRIEF
SKY77550
(1) RX
(6) ANT
(19) RX1
0187_001
Only for training and service purposes