Buck-boost converter

A buck-boost converter, the AS1331, that provides continuous transitions between buck and boost mode making it suitable for dual- or triple-cell alkaline/Ni-Cad/NiMH as well as single-cell Li-Ion battery applications, has been introduced by austriamicrosystems.

The device offers an adjustable output voltage range from 2.5 to 3.3 from an input voltage range of 1.8 to 5.5. To reduce external part count as well as PCB space, fixed output voltage variants of 2.5, 3.0 and 3.3 with ±3% accuracy are also available.

From a Li-Ion battery input voltage range, the converter offers 300 mA output. Combined with two small capacitors and a single chip-scale inductor, it provides a small and low-profile footprint for battery-powered applications.

The device has a four-switch architecture to deliver efficiencies of up to 90% while, at light loads, the quiescent current is reduced to 22 µA. In shutdown mode it disconnects the input from the output drawing only 100 nA shutdown current. The converter offers battery monitoring circuitry which can also be used for power-OK signalling.

To prevent excessive inrush current during start-up, the device has a soft-start feature plus additional features such as overload protection and thermal shutdown circuitry.