Freescale Semiconductor introduced three high power LDMOS Radio Frequency Integrated Circuits (RFIC) that allow designers of RF power amplifiers for WiMAX base stations to reduce costs, form factors and part counts. The devices also increase performance and reliability when compared with amplifiers employing discrete RF power transistors.
The new devices extend Freescale’s portfolio of RFICs to the two primary bands utilized by WiMAX throughout the world, and are the first RFICs available in over-molded plastic packages operating at these frequencies.
Operating in the 2.7 GHz and 3.5 GHz WiMAX bands, the devices are the first WiMAX RFICs to leverage the cost and mechanical stability advantages of over-molded plastic packages. They are also the first such devices to integrate multiple gain stages into a single packaged device.
The MW7IC2725N and MW7IC2750N RFICs operate from 2.3 to 2.7 GHz, and the MW7IC3825N operates from 3.4 to 3.6 GHz. All three use Freescale’s seventh-generation high-voltage (HV7) LDMOS process technology, which has been deployed worldwide in both discrete field effect transistors, as well as in RFICs for wireless applications operating at 900 MHz and 2 GHz.
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. The use of RFICs has significant advantages over this traditional approach. By integrating two stages of gain in a single package, RFICs reduce the number of required individual devices. In most cases, the higher RF output power of the new RFICs allows for the elimination of the predriver stage in WiMAX. The devices can also be used along with discrete LDMOS FETs to produce even higher RF output power.
The RFICs 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. This minimizes board space and reduces design complexity. System cost savings are further compounded when combined with the inherent cost savings of approximately 25 percent provided by over-molded plastic packaging versus traditional metal ceramic air-cavity packages.
“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,” said Gavin P. Woods, vice president and general manager of Freescale Semiconductor’s RF Division. “Our new RFICs can play a key role in this critical cost reduction. Our parts not only reduce amplifier cost, size and complexity by integrating multiple gain stages in a single device, they also offer the inherent cost savings of over-molded plastic packaging as well.”
Key specifications for the new Freescale RFICs are:
• MW7IC2725N: 25 W CW output power at 1 dB gain compression point (P1dB) and at 4 W average power; 28 dB gain, 17% efficiency, Adjacent Channel Power Ratio (ACPR) at 5.25 MHz offset of -50 dBc in 500 kHz channel bandwidth.
• MW7IC2750N: 50 W CW output power at 1 dB gain compression point (P1dB) and at 8 W average power; 26 dB gain, 17% efficiency, Adjacent Channel Power Ratio (ACPR) at 5.25-MHz offset of -49 dBc in 500 kHz channel bandwidth.
• MW7IC3825N: 25 W CW output power at 1 dB gain compression point (P1dB) and at 5 W average RF output power; 23.5 dB gain, 15% efficiency, Adjacent Channel Power Ratio (ACPR) at 5.25 MHz offset of -49 dBc in 500 kHz channel bandwidth.
These devices operate from a 28 to 32 VDC supply and are extremely rugged, with the ability to handle a VSWR of 10:1 at 32 VDC while delivering their rated CW output power.
With the use of Freescale’s innovative over-molded plastic packaging, the RFICs also have tight mechanical tolerances, enabling designers to maintain the high manufacturing yields required at WiMAX frequencies, which have been difficult to achieve when using traditional discrete devices.
The RFICs incorporate electrostatic-discharge (ESD) protection, making them less susceptible to damage during the manufacturing process. This ESD protection enables a greater negative gate-source voltage swing, which improves device performance when operating in Class C mode.
The MW7IC2725N, MW7IC2750N, MW7IC3825N are sampling now and full production is expected in Q1, 2008.