Freescale introduces RF power devices and reference designs for emerging TD-SCDMA wireless networks

Freescale’s advanced high-efficiency devices include the MRF7P20040H LDMOS FET and the MD7IC2050N multi-stage integrated power amplifier IC. Freescale’s simultaneous introduction of two reference designs based on Doherty architecture speeds manufacturers’ ability to create compact, cost-effective, high performance base station transceiver products for TD-SCDMA networks.

“Freescale continues its leadership in LDMOS RF technology by offering high performance solutions for customers using TD-SCDMA wireless technology in China,” said Gavin Woods, vice president and general manager of Freescale's RF Division. “Freescale is applying its knowledge and leadership in RF power technology to support the specific requirements of TD-SCDMA as the technology is rapidly deployed throughout China.”

Freescale’s latest RF LDMOS devices make it possible to build RF power amplifiers that are optimally suited to a chosen design. The designer can select a discrete, three-stage PA configuration with the MRF7P20040H as the final amplifier, or the MD7IC2050N IC (which includes the driver and final amplifier stages) in a two-stage PA configuration. Both devices are extremely well suited for use in Doherty amplifiers, which are universally employed in today’s base station transceivers. A Doherty amplifier consists of two amplifiers that operate under different transmit-signal conditions and typically require separate transistors for each amplifier.

However, Freescale’s MRF7P20040H and MD7IC2050N support a dual-path configuration, which allows a Doherty amplifier to be constructed using a single device rather than two for the final-stage amplifier. In addition, since both devices are inherently broadband, they can operate in both bands allocated for TD-SCDMA (1880 to 1920 MHz and 2010 to 2025 MHz), so the same device can be used to provide RF power in both bands. Together, these advantages can significantly reduce a TD-SCDMA amplifier’s size, bill-of-materials and circuit complexity, while also simplifying inventory management.

Freescale’s introduction of two Doherty amplifier reference designs can significantly shorten the amplifier design cycle. The first employs Freescale’s MMG3014N general-purpose amplifier driving the MD7IC2050N to produce a two-stage IC-based lineup that delivers 35 percent efficiency at 10 W average RF output and a total gain of 45 dB. The second employs Freescale’s MMG3014N as the pre-driver, the MW6S004N LDMOS FET as the driver and the MRF7P20040H as the final amplifier stage. The result is a three-stage, discrete-based lineup that delivers 38 percent efficiency at 10 W average RF output and 50 dB of total gain.

Other key features of the two devices, including typical Doherty performance as measured with a six-carrier, 2025 MHz TD-SCDMA, are as follows:

• MRF7P20040HS: 50 W peak RF output power; drain efficiency of 43 percent; 18 dB gain at 10 W average output power; and air-cavity ceramic package with internal matching for ease of use.

• MD7IC2050N: 70 W peak RF output power; drain efficiency of 35 percent; 29 dB gain at 10 W average output power; and on-chip quiescent current temperature compensation with 50 ohm on-chip input matching in a 225 degree C capable over-molded plastic package.

Both RoHS-compliant devices are production tested in a symmetrical Doherty amplifier configuration for guaranteed RF power output and incorporate Electro-Static Discharge (ESD) protection that provides resistance to damage caused by stray energy encountered on assembly lines.