Low-Noise 650-mA DC-DC Buck Regulator Targets Wireless Devices

High efficiency and tiny packaging make the AS1339 buck regulator well suited for multiband WCDMA/NCDMA applications, such as cellular handsets, wireless PDAs, and smart phones. The AS1339 delivers up to 650 mA from an input voltage range of 2.7 to 5.5 V, ideal for use with single Li-Ion cells. To improve battery lifetime, low-power RF amplifiers can scale the output power dynamically by changing its supply voltage. Output voltage is dynamically controlled using an external analog input signal. The 30-µs settling time of the output voltage ensures CDMA-specifications are not exceeded. A 2-MHz fixed switching frequency minimizes the PCB footprint by allowing the use of tiny low-profile inductors and capacitors. With 97% peak efficiency, the AS1339 boosts battery lifetime in any application. Supporting 1.1 A of peak current, the integrated 110-m? bypass FET provides maximum power with minimum dropout. The AS1339 integrates two 10-mA low-noise, high-PSRR LDOs, ideal for PA biasing. Each LDO features a separate enable, provides high output voltage accuracy, and requires only 10 nF of output capacitance. If the supply is not required, the AS1339 offers a 100-nA shutdown mode combined with an output disconnect feature. The AS1339 is available in a 2-mm x 2-mm 16-pin WL-CSP covering the industrial temperature range of -40°C to +85°C. Pricing is set at $1.49 each in 1000-unit lots. AUSTRIAMICROSYSTEMS AG, Unterpremstaetten, Austria. +43 3136 500-0.