SKY74218

• Closed Polar Loop transmitter
• No delay adjustment required
• Simplified control interface with channel and PCL programming
• Compatible with the DigRF v1.12 interface
• Low external component count

RF transceiver for quad-band GSM, GPRS, and EDGE Applications

The SKY74218 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 RadioService (GPRS), and Enhanced Data Rate for GSM Evolution(EDGE) handsets and modules. The Helios 3D EDGE RFSubsystem supports GSM850, EGSM900, DCS1800, andPCS1900 applications.

The receiver SKY74218 consists of four integrated Low Noise Amplifiers(LNAs), a quadrature demodulator, and selectable baseband filterbandwidths.

The low Intermediate Frequency (IF) receive architectureincorporates digital back-end filtering. Analog signals areconverted into a digital representation suitable for Digital SignalProcessor (DSP) operations. The timing and control section of theSKY74218 generates a 26 MHz high-stability clock for use onchipand a 26 MHz signal (SYSCLK) supplied to the baseband.Three additional reference clocks of SKY74218 are also available.The device also generates a number of internal General PurposeInputs/Outputs (GPIOs) used for timing and control, and an analogsignal to control the PA output power.

The SKY74218 implements Skyworks closed Polar Loop transmitarchitecture. This architecture, while maintaining the traditionalanalog In-Phase and Quadrature (I/Q) signals, autonomously splitsthe amplitude and phase within the device. The filter-savingadvantage of the translation-loop approach is embedded in thearchitecture. Also included is an AM loop that provides both signalAM and power level control.

The SKY74218 features an integrated, fully programmable, fractional-N synthesizer suitable for EGPRS multi-slot operation.The reference frequency for the synthesizer is supplied by anintegrated Capacitance Controlled Crystal Oscillator (CCXO) circuitthat enables the use of a low-cost crystal. The CCXO alsoprovides a buffered reference frequency output to supply otherdevices in the system.

The SKY74218 is intended to be used with Skyworks SKY77524Front-End Module (FEM) (Data Sheet #200638), which contains aswitch, PA, and an integrated coupler for use with Skyworksclosed Polar Loop EDGE architecture. Together, the transceiverand FEM form the Helios 3D EDGE RF Subsystem.

The SKY74218 is packaged in a small, 44-pin 5 x 5 mm dual-rowRF Land Grid Array (RFLGA) package.