SKY77531 Datasheet, PDF (1/2 Pages) Skyworks Solutions Inc. – PHEMT RF switch affords high linearity

PRODUCT SUMMARY
SKY77531 Tx–Rx iPAC^™ FEM for Quad–Band GSM/GPRS
Applications
• Quad-band cellular handsets
encompassing
- Class 4 GSM850/900
- DCS1800/PCS1900
- Class 12 GPRS multi-slot
operation
Features
• High efficiency
- 48% (GSM850/900)
- 41% (DCS1800/PCS1900)
• Low transmit supply current
- 1.26 A (GSM850/900)
- 0.90 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
• TX harmonics below –33 dBm
• PHEMT RF switch affords high
linearity, low insertion loss,
and less than 20 μA supply
current in receive modes
• Small outline: 6 mm x 8 mm
• Low profile: 1.05 mm
• Compatible with multiple logic
families
• Low APC current: 25 μA
Description
The SKY77531 is a transmit and receive front-end module (FEM) with Integrated Power Amplifier
Control (iPAC^™) for quad-band cellular handsets comprising GSM850/900 and DCS1800/PCS1900
operation. Designed in a low profile, compact form factor, the SKY77531 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, 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 band and the other PA block supports the DCS1800/PCS1900 band. 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 a PHEMT RF switch. The
GaAs die, PHEMT die, Silicon (Si) 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 pads, BS1 and BS2, select CEL,
GSM, DCS and PCS modes of operation. Transmit enable TX_EN and transmit switch enable
TX_SW_EN control receive or transmit mode of the RF switch (TX = logic 1). Proper timing
between transmit enable TX_EN 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 SKY77531 is compatible with logic levels from 1.2 V to VCC for BS1, BS2, TX_EN, and
TX_SW_EN pads, depending on the level applied to the VLOGIC pad. This feature provides
additional flexibility for the designer in the selection of FEM interface control logic.
Figure 1. SKY77531 Functional Block Diagram
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [e-mail] • www.skyworksinc.com
200644A • Skyworks Proprietary and Confidential Information • Products and Product Information are Subject to Change Without Notice. • February 6, 2007