SKY77551

Tx-Rx FEM for Quad-Band GSM / GPRS / EDGE - Triple-Band WCDMA Antenna Switch Support

Please note: this product is being discontinued and is not recommended for new designs.

SKY77551 is a transmit and receive Front End Module (FEM) designed in a very low profile (0.9 mm) and compact form factor for quad-band cellular handsets comprising GSM850/900, DCS1800, and PCS1900 operation — a complete transmit VCO-to-Antenna and Antenna-toreceive SAW filter solution. The FEM also supports Class 12 General Packet Radio Service (GPRS) multi-slot operation and linear EDGE operation. WCDMA switch-through support is provided by three dedicated high-linearity ports.

The module consists of a GSM850/900 PA and DCS1800/PCS1900 PA block, impedancematching circuitry for 50 Ω input and output impedances, Tx harmonic filtering, a high linearity/low insertion loss switch, and a CMOS Power Amplifier Control (PAC) block. A custom silicon integrated circuit contains decoder circuitry to control the RF switch while providing a low current, external control interface.

Fabricated in InGaP/GaAs, the Heterojunction Bipolar Transistor (HBT) PA blocks support the GSM850/900 bands and DCS1800/PCS1900 bands. Both PA blocks share common power supply pads to distribute current. The output of the PA block and the outputs to the seven receive pads connect to the antenna pad through a high-linearity antenna switch. The WCDMA and Rx ports feature a 0 volts DC offset level which eliminates the need for external blocking capacitors. The InGaP/GaAs die, switch die, Silicon (Si) controller die, and passive components are mounted on a multi-layer laminate substrate and the entire assembly is encapsulated with plastic overmold.

RF input and output ports of the SKY77551 are internally matched to a 50 Ω load to reduce the number of external components on the phone board. Extremely low leakage current of the FEM maximizes handset standby time. Control of transmit and receive RF signal flows, and band selection are performed by four external control pads (see Figure 1 on overleaf). Mode of operation, Tx vs. Rx, and Band (GSM850, GSM900, DCS1800, and PCS1900) are controlled with the four logic inputs: Mode, TxEN, BS1, and BS2. Proper timing of the TxEN input and the VRAMP input ensures high isolation between the antenna and Tx-VCO while the VCO is being tuned prior to the transmit burst. All logic control inputs returned to a standby state (0 V) ensure ETSI compliance to the harmonics specification.

The integrated power amplifier control (PAC) function provides envelope amplitude control by reducing sensitivity to input drive, temperature, power supply, and process variation. Output power variation into mismatch is minimized with Skyworks’ True Power control circuit.

Product Summary

Talk to Sales ECAD Model

Specifications

Frequency (MHz)

824-849
880-915
1710-1785
1850-1910

DescriptionTx-Rx FEM for Quad-Band GSM/GPRS/EDGE
- Triple-Band WCDMA Antenna Switch Support
GSM850
GSM900
DCS1800
PCS1900

Typical Output Power (dBm) GSM

34.0
34.0
31.2
31.2

Typical PAE (%)

45
45
40
40

Supply Voltage (V)3.0-4.6

PackageMCM, 28-pin

Package (mm)6 x 6 x 0.9

Features

Small, low profile package: 6 mm x 6 mm x 0.9 mm, 28-pad configuration
Low input power range: –1 to 6 dBm
High efficiency: 45% GSM850, 45% GSM900, 40% DCS1800, 40% PCS1900
Tx-VCO-to-antenna and antenna-to-Rx-SAW filter RF interface
Tx harmonics below –38 dBm
Current limiting for over-voltage protection and extended battery life
Input/Output matched internally to 50 Ω
High impedance control inputs: 20 μA, maximum
Input control circuitry built-in for improved TRP variation

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