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RF5725

DS120214

7628 Thorndike Road, Greensboro, NC 27409-9421 · For sales or technical

support, contact RFMD at (+1) 336-678-5570 or sales-support@rfmd.com.

Theory of Operation

The RF5725 FEM is a single-chip integrated front-end module (FEM) for high performance WiFi applications in the 2.4GHz to

2.5GHz ISM band. The FEM greatly reduces the number of external components minimizing footprint and assembly cost of the

overall 802.11b/g solution. The RF5725 has an integrated b/g power amplifier, LNA, a Couple Power Detector, and TX filtering.

It is also capable of switching between WiFi RX, WiFi TX, and BTH RX/TX operations. The device is manufactured using GaAs

HBT and pHEMT processes on a 3mmx3mmx0.5mm 16-pin QFN package. The module meets or exceeds the RF front-end

needs of the 802.11b/g WiFi RF systems.

The RF5725 is a very easy part to implement, but care in circuit layout and component selection is always advisable when

designing circuits that operate at high frequencies. To reduce the design and optimization process on the customer applica-

tion, the evaluation board layout should be copied as close as possible, in particular the ground and via configurations. Gerber

files of RFMD PCBA designs can be provided upon request. The supply voltage lines should present an RF short to the FEM by

using bypass capacitors on the VCC traces. Please contact RFMD Sales or Application Engineering for additional data and guid-

ance.

To simplify bias conditions, the FR5725 requires a single positive supply voltage (VCC), a positive current control bias (VREG)

supply, and a positive supply for switch control. The built in Coupler Power Detector of the FR5725 is very accurate and mini-

mizes calibration time in the system. All inputs and outputs are internally matched to 50

.

Transmit Path

The RF5725 has a typical gain of 28dB form 2.4GHz to 2.5GHz, and delivers 17dBm typical output power under 54Mbps

OFDM modulation and 21dBm under 1Mbps 11b modulation. The RF5725 requires a single positive of 3.3V to 4.2V to oper-

ate at full specifications. Current control optimization for the 802.11b/g band is provided through one bias control input pin

(VREG). The VREG pin requires a regulated supply to maintain nominal bias current.

Out of Band Rejection

The RF5725 contains basic filtering components to produce a bandpass response for the transmit path. Due to space con-

straints inside the module filtering is limited to a few resonant poles. Depending upon the end-user’s application, additional fil-

ters may be needed to meet the out of band rejection requirements of the system.

Receive Path

The 802.11b/g path has a 50

 single-ended port with a nominal gain of 10dB in WiFi RX mode and 6dB in WiFi RX/BT mode.

The Receive port return loss is 9.6dB minimum. The RF5725 is designed so that the SP3T may act as a 3dB splitter when

placed in the WiFi RX and BT RX mode. In this mode, the FEM can receive Bluetooth™ and WiFi signals simultaneously with an

additional 3dB of loss.