Fem With Integrated Power Amplifier Module - LG -A270 Service Manual

3.3 FEM with integrated Power Amplifier Module (SKY77550, U300)
3.3 FEM with integrated Power Amplifier Module (SKY77550, U300)
3.3.1 Internal Block Diagram
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
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 12 General Packet Radio Service (GPRS) multi-slot
operation. The module consists of a GSM850/900 PA block and a DCS1800/PCS1900 PA block,
impedancematching 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 Heterojunction Bipolar Transistor (HBT) PA blocks, a BiFET 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. Both PA blocks share common power supply pads to
distribute current. The output of each PA block and the outputs to the two receive pads are connected to the
antenna pad through an RF switch. The GaAs die, Switch die and passive components are mounted on a
multi-layer laminate substrate. The assembly is encapsulated with plastic overmold.
LGE Internal Use Only
LGE Internal Use Only
HBT POWER AMPUFLER
CURRENT SENSE
POWER AMPLIFIER CONTROL
LOGIC DECODER
Figure. 3.3.1 SKY77550 FUNCTIONAL BLOCK DIAGRAM
Match
Match
Copyright © 2012 LG Electronics. Inc. All right reserved.
19
O nly for training and service purposes
-  - Copyright © 01 LG Electronics. Inc. All right reserved.
3. TECHNICAL BRIEF
3. TECHNICAL BRIEF
SKY77550
(1) RX
(6) ANT
(19) RX1
01138_001
Only for training and service purposes