SKY77529

• WCDMA pass-through - 4 linear ports
• TRP-compliant design
• SPI bus support
• Low loss PHEMT RF antenna switch
• Detector output: linear V/V
• Closed loop GMSK mode power control
• Small outline - 7.5 x 7 mm
• Low profile - 0.9 mm MAX.
• Gold-plated, lead-free contacts
• Low VRAMP current

Tx Front-End Module for Quad-Band GSM / EDGE

The SKY77529 Tx Front End Module (FEM) is designed in a compact form factor for quad-bandcellular handsets comprising GSM850/900, DCS1800, PCS1900, supporting GMSK and linear EDGEmodulation. Class 12 General Packet Radio Service (GPRS) multi-slot operation is also supported.

The module SKY77529 consists of a GSM850/900 PA block and a DCS1800/PCS1900 PA block, a printeddirectional coupler for each block impedance-matching circuitry for 50 input and outputimpedances, a multifunction power amplifier control (MFC) block, low pass harmonic rejection filters,and an SP8T Antenna T/R switch. The T/R switch of SKY77529 incorporates four linear ports to allow WCDMAparallel operation.

Two separate Heterojunction Bipolar Transistor (HBT) PA blocks of SKY77529 are fabricated onto an InGaP die; onesupports the GSM850/900 bands, the other supports the DCS1800 and PCS1900 bands. The InGaP PAdie, the silicon MFC die, PHEMT switch die, and the passive components are mounted on a multi-layerlaminate substrate. The assembly of SKY77529 is encapsulated with plastic overmold.

The FEM SKY77529 incorporates full support for a Serial Peripheral Interface (SPI) bus function. The SPIcontroller shall accept SPI telegrams with data fields that support PA and switchplexer-relatedfunctions. All FEM operating modes and switch states shall be determined by the SPI telegram.

The Multi-function Control (MFC) of SKY77529 provides for interoperation with a specified transceiver that willestablish a closed loop power control mechanism. The external circuit uses the Linear Detector outputto set a fixed bias point for 8PSK (EDGE) mode and a variable bias point for GMSK (GSM) mode. Thepower control loop together with the MFC will reduce sensitivity to antenna load, input drive,temperature, power supply, and process variation. The combined circuit of SKY77529 configures the PA for fixedgain in 8PSK mode while providing the ability to optimize the PA bias at different power levels tomaximize efficiency.