SKY77524

• Closed Polar Loop? EDGE Power Amplifier
• High efficiency
• Integrated coupler
• Integrated transmit/receive antenna switch
• Input/output matching

Tx/Rx FEM w/Integrated Coupler for Quad-Band GSM and EDGE Applications

The SKY77524 Digital RF (DigRF) Transceiver is a highlyintegrated device designed for Skyworks Helios? 3D EDGE RFSubsystem. This subsystem is intended for quad-band GlobalSystem for Mobile Communications (GSM), General Packet RadioThe SKY77524 is a transmit/receive Front-End Module (FEM)designed for Skyworks Helios? 3A and 3D EDGE RF Subsystems.These subsystems are intended for multi-band Global System forMobile Communications (GSM), General Packet Radio Service(GPRS), and Enhanced Data Rate for GSM Evolution (EDGE)handsets and modules. Both subsystems of SKY77524 support GSM850,EGSM900, DCS1800, and PCS1900 applications.

The Helios 3A subsystem (which includes the SKY74219 RFTransceiver) of SKY77524 provides an analog control interface. The Helios 3Dsubsystem (which includes the SKY74218 RF Transceiver)provides a digital (DigRF) control interface.

The SKY77524 provides a complete transmit path fromtransceiver output to antenna. The module has impedancematchingcircuitry for 50 inputs and outputs, and integratestransmit harmonic filtering, an integrated coupler, and highlinearityand low insertion-loss pHEMT RF switches. A customBiCMOS integrated circuit SKY77524 provides the internal PAC function,interface circuitry, and decoder circuitry to control the RFswitches.

Two Heterojunction Bipolar Transistor (HBT) PA blocks of SKY77524 arefabricated onto an Indium Gallium Phosphide (InGaP) die; oneblock supports the GSM850 and EGSM900 bands, the othersupports the DCS1800 and PCS1900 bands. Both PA blocks sharecommon power supply pins to distribute current. Outputs from thePA blocks and four receive pins connect to the antenna usingpHEMT RF switches. The InGaP die, the Silicon (Si) die, thepHEMT die, and the passive components SKY77524 are mounted on a multilayerlaminate substrate, and the entire assembly encapsulatedwith plastic overmold.

Three external control pins of SKY77524 facilitate band selection, and control ofthe transmit and receive RF signal flows. Pin signals BS0 and BS1select GSM850, EGSM900, DCS1800, or PCS1900 modes. TheTR_EN pin signal selects the transmit or receive mode of therespective RF switch. Proper timing of the pin signal logic andpower control (the VPC pin) allows high isolation between theantenna and the radio transceiver output.

The PAC_EN signal of SKY77524 enables the PAC circuitry to minimize batterydrain. The low leakage current (6.5 µA, typical) of the dual PAmodule maximizes handset standby time.

Feedback signals from the SKY77524 to the transceiver form anintegral portion of the Skyworks Polar Loop? architecture. Thisarchitecture autonomously splits amplitude and phase using thetraditional analog In-Phase and Quadrature (I/Q) signals. Thefilter-saving advantage of the translation-loop approach isembedded in the architecture. Also included is an AM loop thatprovides both signal AM and power level control.