RF power DC-DC converter offers smallest power management solution for W-CDMA/CDMA RFPAs in 3G handsets

Winchester, UK - Fairchild Semiconductor is claiming the industry's smallest power management solution for the designers of 3G handsets and wireless datacards with the introduction of the company's FAN5902, RF Power DC-to-DC converter which operates at 6 MHz with a reduced size 0.5 uH chip inductor that saves space and component costs.

The new converter, which is packaged in a 12 bump, 0.5 mm pitch CSP package, helps to extend talk-time by up to 40 minutes in 3G handsets by adapting the voltage supply level of the 3G RF power amplifier according to the RF power sent through the antennae, enabling higher power efficiency for a wide range of antenna power levels. This results in up to 100 mA of battery current consumption savings in data-centric and smart phones especially in suburban and poor coverage areas. The feature enables 20 to 30 percent more power, extending connection time and allowing 3G handsets to run more processor applications. In addition, the FAN5902 offers up to 800 mA rms current output capability to service excessive RF PA current resulting from strong antenna mismatch and a 50 milliohm on resistance bypass FET, enabling operation down to 2.7 V.

"The new FAN5902 is the first in a product family of devices that will see other new introductions later this year and during next year," explained Ingrid Kugler, Fairchild Semiconductor's regional market manager responsible for mobile phone business. "The device was designed by Fairchild's Santa Fe-based design team focused on power management solutions."

Commenting on the space saving benefits of the new device Kugler, said: "By using high frequency switching technology we can make use of small inductors. The 6 MHz PWM synchronous operation is key because it enabled our team to design in a small 0402 capacitor as well as have a low cost, smaller sized inductor".

Kugler pointed out that consumers are demanding that their 3G phones deliver more connection time, longer talk time and extended high speed data (Internet) connection time. However, at the same time phone users also desire more functionality such as larger displays and faster processors to handle the data-centric applications more easily. W-CDMA/CDMA RFPAs in 3G handsets can consume up to 60 percent of the phone power in bad coverage areas.

"For users of smart phones, the FAN5902 means better coverage in poor coverage areas, longer talk time and a better consumer experience," commented Kugler. "We believe 3G is still a growing market. Higher data content is the trend. If people buy new phones they go for feature-rich phones these days to handle all the new multimedia facilities. Phones are replacing laptops by offering more 'surfing', file transfers and data-rich applications. People are now used to small mobile phones but they also want more features in their phones. They want the same small sized phones but they want to have more capabilities integrated into these handheld devices. High speed data transmission can drain a battery very quickly. When a mobile phone enters 'battery full' mode they can waste a lot of energy and begin to heat up the PCB and that reduces the lifetime of the battery and the whole phone."

The FAN5902 addresses the key problem of overheating in the RF power amplifier, especially at high battery voltage. The FAN5902 improves the RFPA efficiency by using Dynamic Voltage Scaling (DVS) techniques to scale down the RFPA supply voltage and reduces its heating by 20 to 40 percent. As a result the heat sink can be shrunk and the component density can be increased, reducing weight, cost and size.

Availability and Pricing

Samples are available now and are priced at $0.75 in 1,000-unit pieces.

Datasheet for: FAN5902

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