96% efficient 1A buck converter for single-cell Li-ion supplies

April 23, 2015 // By Graham Prophet
Longer run-times are promised for single-cell Li-ion battery applications; ams’ AS1382’s small footprint and 4 MHz switching frequency enable implementation of very small power circuits in mobile phones and wearables

This 1A synchronous buck converter has the wide input voltage range, high efficiency and low stand-by current required in designs powered by a single-cell lithium-ion battery, ams says.

The AS1382 step-down converter operates from an input range of 2.7-5.5V, and provides an output down to as little as 0.6V. Offering efficiency as high as 96% and no-load current of 95 µA, the converter helps designers of li-ion battery powered devices to reduce losses in the power circuit and to extend their product’s run-time between charges. In shut-down mode, the device draws 0.04µA.

Housed in a 1.22 x 0.85 mm six-lead chip-scale package (WL-CSP6) with a 0.4 mm pitch, the AS1382 operates at an internally fixed frequency of 2 MHz, 3 MHz or 4 MHz, enabling the use of a small inductor. The AS1382 has variants offering a fixed output of 1.0V, 1.2V, 1.5V or 1.8V, and a version with an output adjustable over the range 0.61-3.35V. All support a continuous load current of 1A, and require an output capacitor of 10 µF.

The step-down converter may be operated in one of two modes: its Low-Ripple/Low-Noise mode produces very low levels of ripple and noise. In High-Efficiency mode, the device has lower power losses when supplying light loads, increasing stand-by time in always-on battery operation.

The device includes an internal synchronous switch, which eliminates the need for an external Schottky diode.

The DC-DC step-down converter AS1382 is priced at $0.21 (1000). An evaluation board for the AS1382 is available online.

ams; www.ams.com/step-down-converter/AS1382