austriamicrosystems Unveils Low Noise 650mA DC-DC Buck Regulator with Two LDOs for RF PAs

(Product News, 20 Jul 2009)

austriamicrosystems, a designer and manufacturer of high performance analog ICs for communications, industrial, medical and automotive applications, has launched the AS1339 step down regulator. High efficiency and tiny packaging make the AS1339 ideal for multiband W-CDMA/NCDMA applications, such as cellular handsets, wireless PDAs and smart phones.

The AS1339 delivers up to 650mA from an input voltage range of 2.7 to 5.5V making the device ideal for single Li-Ion cells. To improve battery lifetime low power RF amplifiers can scale the output power dynamically by changing its supply voltage. To support this, the output voltage of the
AS1339 is dynamically controlled using an external analogue input signal which has a gain of 2.5V/V. Additionally, the extremely fast 30µs settling time of the output voltage ensures CDMA-specifications are not exceeded.

Housed in a 2x2mm WL-CSP, the AS1339 is designed for minimal space requirements in size restricted battery powered applications such as mobile phones and other portable wireless end equipment. The 2MHz fixed switching frequency minimizes the PCB footprint by allowing the use of tiny low profile inductors and capacitors. This constant frequency switching results in low predictable output noise which is additionally reduced by the internal noise reduction circuitry.

“Power efficiency combined with reduced external component size and cost is the key behind the AS1339 buck converter,” said Bruce Ulrich, marketing director Standard Linear at austriamicrosystems.” austriamicrosystems’AS1339 is the perfect symbiosis between efficiency and analog performance.
Thanks to its small size and fast switching speed, only a minimum of PCB space is required. Combined with the unique low noise circuitry, this part is the way to go for high efficiency RF PA designs.”

With 97 percent peak efficiency, the AS1339 boosts battery lifetime in any application. Supporting 1.1A of peak current, the integrated 110mΩ bypass FET provides maximum power with minimum dropout under even low-battery conditions. The AS1339 enters bypass mode automatically during high power transmissions. The AS1339 also integrates two 10mA low-noise, high-PSRR LDO’s, making them ideal for PA biasing. Each LDO features a separate enable, provides high output voltage accuracy, and requires only 10nF of output capacitance.

Moreover if the supply is not required, for example, if a mobile phone is in in-flight mode, the AS1339 offers a 100nA shutdown mode combined with an output disconnect feature. Additional features are soft start and safety features such as current overload and thermal shutdown protection.

The AS1339 is available in the tiny 2x2mm WL-CSP 16-bumps covering the industrial temperature range of -40°C to +85°C.