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SKY77555

Tx–Rx FEM Based on CMOS PA for Dual-Band GSM / GPRS (880–915 MHz and 1710–1785 MHz)

Skyworks Solutions 

PRODUCT SUMMARY

SKY77555 Tx–Rx FEM Based on CMOS PA for Dual-Band

GSM / GPRS (880–915 MHz and 1710–1785 MHz)

Applications

• Dual-band cellular handsets

encompassing

- Class 4 GSM900

- DCS1800

- Class 12 GPRS multi-slot

operation

Features

• Efficiency

- 36% GSM (33.0 dBm)

- 29% DCS (30.5 dBm)

• Log linear power control

response with <100 dB/V

power control slope

• Low Rx band noise

• Supply current

- 1.58 A GSM (33.0 dBm)

- 1.10 A DCS (30.5 dBm)

• Fully integrated closed loop

• 50 Ω matched Input/Output

• Tx–VCO-to-antenna and

antenna-to-Rx-SAW filter

RF interface

• PHEMT RF switches afford

high linearity, low insertion

loss, and low current in

receive modes

• Small, low profile package

- 5 mm x 6 mm x 1.05 mm

• Compatible with multiple

logic families

Description

The SKY77555 is a transmit and receive front-end module (FEM) based on CMOS Power Amplifier for

dual-band cellular handsets comprising GSM900 and DCS1800 operation. Designed in a low profile,

compact form factor, the SKY77555 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 GSM900/DCS1800 CMOS PA, Tx harmonics filtering, high linearity and low

insertion loss PHEMT RF switches, and diplexer. The CMOS device integrates a full dual-band

GSM/GPRS power amplifier function. High accuracy power control and ramping is achieved on the

CMOS chip via a closed loop power control system. Current drain is limited under load mismatch

conditions via the nature of the innovative power control circuit. The output of the CMOS PA die and

the outputs to the two receive pads are connected to the antenna pad through PHEMT RF switches

and a diplexer. The CMOS die, PHEMT 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 modes are performed using two external control

pads. Refer to the functional block diagram in Figure 1. The band select pad (BS) selects between

GSM and DCS modes of operation. The transmit enable (TxEN) pad controls the receive or transmit

mode of the respective RF switch (Tx = logic 1). 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 SKY77555 is compatible with logic levels from 1.6 V to 2.8 V for BS and TxEN 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. SKY77555 Functional Block Diagram

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com

201256A • Skyworks Proprietary and Confidential Information • Products and Product Information are Subject to Change Without Notice. • March 3, 2010

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