Dual-input Li-ion battery charger targets handheld apps

Linear Technology Corp. announced an efficient and compact power management solution for handheld applications. The new LTC3550 device incorporates a dual-input Li-ion/Polymer battery charger and a high-efficiency synchronous buck regulator in a 16-lead 3-by-5mm DFN package.

The linear battery charger automatically selects the appropriate power source to efficiently charge single-cell Li-ion batteries via a wall adapter up to 8V (10V abs max) or a USB port. Standalone operation simplifies design, eliminating the need for an external microprocessor for charge termination, said the press release. 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 percent.

The LTC3550's battery charger is equipped with a patented thermal regulation scheme that maximizes the charge rate without the risk of overheating. To preserve battery energy, it draws <6?A from the battery terminal in standby and <1?A in shutdown mode.

The LTC3550's integrated synchronous buck regulator has an adjustable output voltage range of 5.5V to as low as 0.6V, delivering up to 600mA of continuous output current. It uses internal switches with an R_DS(ON) of 0.40 ohm to deliver efficiencies as high as 96 percent, maximizing battery run time. In addition, automatic Burst Mode operation optimizes efficiency at light loads, featuring a quiescent current of 20?A (<1?A in shutdown).

Using a constant frequency current mode architecture, the buck regulator operates from an input voltage range of 2.5V to 5.5V. Its 1.5MHz switching frequency allows the utilization of tiny low cost capacitors and inductors less than 1mm in height. In addition, said the company, the regulator is stable with ceramic output capacitors, achieving low output voltage ripple.

The LTC3550 is available in a 5-by-3-by-0.75mm DFN-16 package. Pricing starts at $2 each for 1,000-piece quantities.