austriamicrosystems AG (austriamicrosystems), a manufacturer of analog ICs, has introduced a new buck-boost converter, AS1331, to its DC-DC product portfolio. The topology of the new converter offers continuous transitions between buck and boost mode making it ideal for dual or triple cell alkaline/NiCad/NiMH as well as single cell lithium-ion (Li-Ion) battery applications. The new AS1331 provides an adjustable output voltage range from 2.5 to 3.3V from an input voltage range of 1.8 to 5.5V.
To reduce external part count as well as PCB space fixed output voltage variants of 2.5, 3.0 and 3.3V with ±3% accuracy are also available. From a Li-Ion battery input voltage range the AS1331 offers 300mA of output current. Combined with two small capacitors and a single chip-scale inductor the AS1331 provides a small and low profile footprint solution, typically required in battery powered applications.
The new AS1331 implements a 4-switch architecture to deliver efficiencies of up to 90% while, at light loads, the quiescent current is reduced down to as low as 22µA, thereby maximizing efficiency. In shutdown mode the AS1331 fully disconnects the input from the output drawing only 100nA shutdown current which further extends battery life time. The AS1331 additionally offers a battery monitoring circuitry which can also be used for power-ok signaling.
In many applications output voltages are in between the input voltage range. Therefore it is a necessary requirement to maintain a constant output voltage as the battery voltage falls below the output, commented Bruce Ulrich, marketing director Standard Linear at austriamicrosystems. The optimized buck-boost architecture of the AS1331 guarantees excellent efficiencies during step-down operation as well as while boosting the input voltage. Pure buck converters stop operation as soon as the input voltage drops below the output voltage. This leaves unused charge in the battery which can be utilized by AS1331 providing up to 25% more battery life time.
To prevent excessive inrush current during startup, the AS1331 offers a soft-start feature plus additional features such as overload protection and thermal shutdown circuitry. The AS1331 is available in a small TDFN (3×3)-10 packages and is suitable for operating temperatures ranging from -40 to +85°C.