Linear Tech Chip Combines Charger and Dual Buck Converters

Linear Technology Corp. has introduced the LTC3552-1, which includes a standalone Li-Ion battery charger and a high efficiency dual synchronous buck regulator housed in a low-profile 3mm x 5mm DFN package. The linear battery charger can deliver up to 950mA charge current from a wall adapter supply, or up to 500mA charge current from a USB supply. The LTC3552-1's two integrated synchronous buck regulators deliver up to 800mA continuous output current at 1.8V, and up to 400mA at 1.575V, respectively.

Standalone operation of the battery charger section simplifies design, eliminating the need for an external microprocessor for charge termination. The final float voltage accuracy is ±1%. The LTC3552-1's battery charger is equipped with a patented thermal regulation scheme that maximizes the charging rate without the risk of overheating. To preserve battery energy, it draws < 2.5uA from the battery terminal in standby and < 1uA in shutdown mode.

The internal switches in the synchronous buck regulators feature an RDS(ON) range of 0.3 Ohm to 0.35 Ohm to deliver efficiencies as high as 92%, maximizing battery run time. In addition, automatic Burst Mode® operation optimizes efficiency at light loads with quiescent current of only 40uA (< 1uA in shutdown).

Using a constant frequency current mode architecture, the buck regulator operates from an input voltage range of 2.5V to 5.5V, making it suited for single-cell Li-Ion/Li-Polymer, multi-cell alkaline or NiMH input applications. Its high 2.25MHz switching frequency allows the utilization of tiny low cost capacitors and inductors less than 1mm in height. Furthermore, the regulator is stable with ceramic capacitors, achieving very low output voltage ripple.

The LTC3552-1 is available from stock in a compact 3mm x 5mm x 0.75mm DFN-16 package. Pricing starts at $2.30 each for 1,000-piece quantities.