PRODUCT SUMMARY
SKY77554-21 Tx Quad-Band / Rx Dual-Band BiFET iPAC™ FEM
for GSM / GPRS (824-915 MHz and 1710-1910 MHz)
w/ Dual WCDMA TRx Switch
Applications
Description
• Dual-band cellular handsets
encompassing
- Class 4 GSM850/900
- DCS1800/PCS1900
- Class 12 GPRS multi-slot
operation
SKY77554-21 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 SKY77554-21 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.
Features
• High efficiency
- 42% (GSM850)
- 42% (GSM900)
- 42% (DCS1800)
- 41% (PCS1900)
• Low transmit supply current
- 1.36 A (GSM850)
- 1.36 A (GSM900)
- 0.86 A (DCS1800/PCS1900)
• Internal ICC sense resistor for
iPAC
• Closed loop iPAC
• 50 Ω matched Input/Output
• Tx–VCO-to-antenna and
antenna-to-Rx-SAW filter RF
interface
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. 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.
Band selection and control of transmit and receive are performed using four external control pads.
Refer to the block diagram in Figure 1 below. The band select pad, BS, selects GSM850, GSM900,
DCS, and PCS modes of operation.
Transmit enable TxEN controls receive or transmit mode of the RF switch (Tx = logic 1) and sets
the turn-on threshold for VRAMP (VRAMP threshold = V(TxEN) ÷ 7). Proper timing between transmit
enable TxEN and Analog Power Control VRAMP allows for high isolation between the antenna and
Tx–VCO while the VCO is being tuned prior to the transmit burst.
The SKY77554-21 is compatible with logic levels from 1.2 V to 2.9 V for BS, TxEN, MODE, and
VSW_EN pads.
• RF switch affords high
linearity, low insertion loss,
and 0 V DC on Rx ports
• Small, low profile package
- 6 mm x 6 mm x 0.9 mm
- 28-pad configuration
Figure 1. SKY77554-21 Functional Block Diagram
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201482A • Skyworks Proprietary and Confidential Information • Products and Product Information are Subject to Change Without Notice. • February 8, 2011
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