The LTC4080X is a complete constant-current/constant-voltage 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 LTC4080X especially suitable for portable applications. Furthermore, the LTC4080X 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 full-featured LTC4080X battery charger also includes automatic recharge and soft-start to limit inrush current. If trickle charging is desired, refer to the LTC4080 datasheet.The LTC4080X 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 LTC4080X is available in 10-lead, low profile (0.75 mm) 3mm × 3mm DFN and 10-lead MSE packages.Trickle ChargePackageLTC4080YesDFN-10LTC4080XNoDFN-10, MS-10ApplicationsWireless HeadsetsBluetooth ApplicationsPortable MP3 PlayersMultifunction Wristwatches