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1 October 2007


Freescale launches multi-stage LDMOS RFICs for 2.7 and 3.5GHz WiMAX base-station PAs

At last week’s 4th WiMAX World USA 2007 event in Chicago, IL, USA, Freescale Semiconductor of Austin, TX, USA introduced three high-power LDMOS silicon RFICs that extend its portfolio to the two primary bands used by WiMAX worldwide (2.7GHz and 3.5GHz). As well as reducing cost, form factor and parts count in RF power amplifiers for WiMAX base-stations, the firm claims, the devices are engineered to also increase performance and reliability compared with amplifiers that use discrete RF power transistors.

The components are the first RFICs available in over-molded plastic packages to operate at these frequencies, Freescale claims, enabling them to leverage cost and mechanical stability advantages. They are also the first such devices to integrate multiple gain stages into a single over-molded plastic packaged device, reducing cost, size and complexity.

The MW7IC2725N and MW7IC2750N RFICs (with output powers of 25W and 50W, respectively) operate at 2.3-2.7GHz, and the 25W MW7IC3825N operates at 3.4-3.6GHz. Working from a 28-32Vdc supply, all three use Freescale’s seventh-generation high-voltage (HV7) LDMOS process technology, which has been deployed in discrete field-effect transistors (FETs) as well as in RFICs for wireless applications operating at 900MHz and 2GHz.

RF power amplifiers employed in WiMAX base-stations typically require three or four stages of amplification, delivered by discrete RF power transistors to achieve the desired output power. Instead, by integrating two gain stages in a single package, RFICs reduce the number of devices required. In most cases, the higher RF output power of the RFICs allows elimination of the pre-driver stage in WiMAX. The devices can also be used along with discrete LDMOS FETs to produce even higher RF output power, says Freescale.

The RFICs can further reduce cost because the capacitors, inductors and resistors required on the circuit board are integrated within the device to provide the same inter-stage impedance matching networks, minimizing board space and reducing design complexity, says Freescale. System cost savings are further compounded when combined with the inherent cost savings of about 25% provided by the over-molded plastic packaging versus current air-cavity packages, the firm adds.

“WiMAX is a very promising technology, but it faces strong competition from existing wireless services, making it essential that WiMAX infrastructure equipment be as cost-effective as possible,” says Gavin P. Woods, VP and general manager of Freescale’s RF Division. “These RFICs can play a key role in this critical cost reduction,” he reckons.

With the use of over-molded plastic packaging, the RFICs are designed to also achieve tight mechanical tolerances, enabling designers to maintain the high manufacturing yields required at WiMAX frequencies, which have been difficult to accomplish using traditional discrete devices, Freescale claims.

The MW7IC2725N, MW7IC2750N and MW7IC3825N devices are sampling now, and full production is expected in Q1/2008.

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