The LTC4081is a complete constant-current/constantvoltage linear battery charger for a single-cell 4.2V lithium-ion/polymer battery with an integrated 300mA synchronous buck converter. A 3mm × 3mm DFN package and low external component count make the LTC4081 especially suitable for portable applications. Furthermore, the LTC4081 is specifically designed to work within USB power specifications.TheCHRGpin indicates when charge current has dropped to ten percent of its programmed value (C/10). An internal 4.5-hour timer terminates the charge cycle. The fullfeatured LTC4081 battery charger also includes trickle charge, automatic recharge, soft-start (to limit inrush current) and an NTC thermistor input used to monitor battery temperature.The LTC4081 integrates a synchronous buck converter that is powered from the BAT pin. It has an adjustable output voltage and can deliver up to 300mA of load current. The buck converter also features low current high efficiency Burst Mode operation that can be selected by the MODE pin.The LTC4081 is available in a 10-lead, low profile (0.75mm) 3mm × 3mm DFN package.ApplicationsWireless HeadsetsBluetooth ApplicationsPortable MP3 PlayersMultifunction Wristwatches