Dual Input Li-Ion Battery Charger with Synchronous 600mA Buck Converter
Linear Technology Corporation announces the LTC3550-1, a power management solution for handheld applications containing a dual input Li-Ion battery charger and a synchronous buck regulator, all housed in a 16-lead 3mm x 5mm dual flat no-lead (DFN) package.
The linear battery charger automatically selects the appropriate power source to efficiently charge single-cell Li-Ion batteries: a wall adapter or a universal serial bus (USB) port, company officials said. Standalone operation simplifies design, eliminating the need for an external microprocessor for charge termination, officials said.
Using a constant-current/constant-voltage algorithm, the charger can deliver up to 950mA of charge current from a wall adapter supply, or up to 500mA of charge current from a USB supply. The final float voltage accuracy is ±0.6% in either case. The LTC3550-1'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 less than 6uA from the battery terminal in standby and less than 1uA in shutdown mode.
The LTC3550-1's integrated synchronous buck regulator can deliver up to 600mA continuous output current. It uses internal switches with an area-specific resistance of only 0.40 Ohm to deliver efficiencies as high as 93%, maximizing battery run time. In addition, automatic Burst Mode® operation optimizes efficiency at light loads, featuring a quiescent current of only 20uA (less than1uA in shutdown), officials said. Using constant frequency current mode architecture, the buck regulator operates from an input voltage range of 2.5V to 5.5V, making it ideal for single-cell Li-Ion or multi-cell alkaline or NiMH input applications, they said. The buck regulator has a fixed output voltage of 1.875V, and its high 1.5MHz switching frequency allows the use of tiny low-cost capacitors and inductors less than 1mm in height. Furthermore, the regulator is stable with ceramic capacitors, achieving low output voltage ripple.
The LTC3550-1 is available from stock in a compact 5mm x 3mm x 0.75mm DFN-16 package. Pricing starts at $2 each for 1,000-piece quantities.
