DESCRIPTION
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 specifi cally designed to work within USB power specifi cations.

FEATURES
■ Complete Linear Battery Charger with Integrated
   Buck Converter in 3mm x 3mm DFN Package

Battery Charger:
■ Constant-Current/Constant-Voltage Operation
   with Thermal Feedback to Maximize Charge Rate
   Without Risk of Overheating
■ Internal 4.5 Hour Safety Timer for Termination
■ Charge Current Programmable Up to 500mA with
   5% Accuracy
■ C/10 Charge Current Detection Output
■ 5µA Supply Current in Shutdown Mode

Switching Regulator:
■ High Effi ciency Synchronous Buck Converter
■ 300mA Output Current (Constant-Frequency Mode)
■ 2.7V to 4.5V Input Range (Powered from BAT Pin)
■ 0.8V to VBAT Output Range
■ MODE Pin Selects Fixed (2.25MHz) Constant-Frequency
   PWM Mode or Low ICC (23µA) Burst Mode®
   Operation
■ 2µA BAT Current in Shutdown Mode

APPLICATIONS
■ Wireless Headsets
■ Bluetooth Applications
■ Portable MP3 Players
■ Multifunction Wristwatches