Buck-boost functionality at the cost of a boost converter

According to the company, the topology of the AS1337 provides an 'innovative step down function', designed to enable buck-boost functionality. The continuous transition between boost and regulated buck mode means that the AS1337 is suitable for single or dual cell applications. The buck-boost converter incorporates an adjustable output voltage range from 2.5 to 5.0V from an input voltage range of 0.65 to 4.5V. From a two cell battery with a voltage range between 1.8 and 3.6V the AS1337 offers 200mA of output current at 3V. austriamicrosystems says that 100mA can be generated from a single cell. Combined with two small capacitors and one chip scale inductor the AS1337 is said to provide a small footprint, low profile solution, typically required in battery powered applications. According to austriamicrosystems, this low voltage DC-DC IC offers power-ok signalling. The AS1337 implements a boost architecture with efficiencies said to be up to 97%, while the converter is designed to be able to enter into buck mode when the input voltage is higher than the output voltage, adopting a buck-boost behavior. In shutdown mode the AS1337B version offers a battery disconnect function, where the input is disconnected from the output, drawing 10nA shutdown current. Bruce Ulrich, marketing director, consumer and communications at austriamicrosystems, said: "Especially in dual cell applications the input voltage can be up to 3.6V when using fresh batteries. Even though this voltage is only available for a very short time, it can damage a 3V system. AS1337 enters a regulated buck mode in order to avoid this problem. A conventional boost converter does not regulate the output voltage in this case. The customer gets buck-boost behaviour at the cost of a standard boost converter. Furthermore, the optimised boost architecture of the AS1337 guarantees excellent efficiencies during step-up operation of up to 97% which is significantly higher than the efficiency of a conventional buck-boost converter." The AS1337 is available in a small TDFN (3x3)-8 package and is suitable for operating temperatures ranging from -40 to 85^°C.