High-performance converters slash power consumption in cell phones by 80%

Santa Clara, CA and Munich, Germany, Nov. 9 — National Semiconductor Corporation announces a new family of DC-DC converters optimized for powering radiofrequency (RF) power amplifiers from a single lithium-ion battery. These new chips from National will enable cell phone makers to reduce power consumption by up to 80 percent, while increasing talk time as much as 90 minutes. The first cell phones to use National's new LM3200 DC-DC converters will appear in the market by year-end.

With 2.5G and 3G wireless handsets gaining popularity, cell phones are becoming a one-stop multimedia station with features such as text messaging, email and software downloads. These new handsets require higher transmit-and-receive rates for (RF) power amplifiers, which mean that they consume more power. Because the RF power amplifier consumes 40 to 60 percent of the overall power budget, reduction of its power consumption will provide a significant increase in the battery life of a handset.

National's new LM3200 is designed specifically to power RF power amplifiers. Compared with previous step-down switchers, the LM3200 has a high switching frequency that allows it to use small external components such as a 2.2 uH inductor. The LM3200 also has an analog voltage-control input that dynamically controls the output voltage of the device depending on the power requirements of the power amplifier. Its bypass operation allows it to support the power amplifier's power requirement during peak usage periods to keep the phone running longer. The converter steps down an input voltage from 2.7V to 5.5V to a variable output voltage from 0.8V to 3.6V, while output voltage is set using a voltage-control analog input for adjusting power levels and efficiency of the RF power amplifier.

“With these new products, National is targeting the power amplifier — a previously unregulated portion of the cell phone — to enable dramatic improvements in battery life and talk time,” said Peter Henry, vice president of National Semiconductor's Portable Power Products Group. “National's LM3200 features a small-size chip-scale package, high switching frequencies and compatibility with a wide variety of industry-standard platform reference designs that will enable our customers to offer phones and other portable devices with outstanding performance.”

Key Technical Specifications of LM3200
The LM3200 offers four modes for mobile phones and similar RF PA applications. Fixed-frequency pulse-width modulator (PWM) mode minimizes RF interference and provides efficient performance under typical operating conditions. Forced bypass mode turns on an internal bypass switch to power the PA directly from the battery. Automatic bypass mode minimizes dropout by turning on the bypass switch when the battery decays close to the output voltage. Shutdown mode turns the device off and reduces battery consumption to 0.1uA (typ.). The LM3200 is designed on National's CMOS7 process, built at National's plant in South Portland, Maine, and tested and assembled at the company's facility in Melaka, Malaysia.

National's LM3200 is available in a 10-pin lead-free micro SMD that measures only 2.2 mm by 1.8mm. A high switching frequency (2MHz) allows use of tiny surface-mount components. Only three external components, a 2.2uH inductor and two 10uF ceramic capacitors, are needed to complete the application circuit. National's LM3200 is priced at $1.60 each in quantities of 1,000 pieces.

National Semiconductor Corporation
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