Linear Technology Corporation announces the LTC3550-1, an efficient, compact power management solution for handheld applications containing a dual input Li-Ion battery charger and a high efficiency synchronous buck regulator, all housed in a low-profile 16-lead 3mm x 5mm 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 USB port. Standalone operation simplifies design, eliminating the need for an external microprocessor for charge termination. 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 which maximizes the charging rate without the risk of overheating. To preserve battery energy, it draws <6uA from the battery terminal in standby and <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 RDS(ON) 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 (<1uA in shutdown). 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. The buck regulator has a fixed output voltage of 1.875V, and its high 1.5MHz 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 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 $2.00 each for 1,000-piece quantities.

 
 
Summary of Features: LTC3550-1 
 Charges Single-Cell Li-Ion Batteries from Wall Adapter & USB Inputs
 
 Automatic Input Power Detection & Selection
 Charge Current Programmable up to 950mA from Wall Adapter Input
 
 High Efficiency 600mA Synchronous Buck Regulator
 No External MOSFET, Sense Resistor or Blocking Diode Needed
 Thermal Regulation Maximizes Charging Rate without Overheating
 
 Preset Charge Voltage with ±0.6% Accuracy 
 Programmable Charge Current Termination
 1.5MHz Constant Frequency Operation (buck converter)
 18uA Suspend Current in Shutdown
 Independent "Power Present" Status Outputs 
 Charge Status Outputs 
 Automatic Recharge 
 Thermally-Enhanced, Low Profile (0.75mm) 16-Lead 3mm x 5mm DFN package