General Description
The LTC4054 is a complete constant-current/constantvoltage linear charger for single cell lithium-ion batteries.
Its ThinSOT package and low external component count make the LTC4054 ideally suited for portable applications. Furthermore, the LTC4054 is s pecifically designed to work within USB power specifications.No external sense resistor is needed, and no blockingdiode is required due to the internal MOSFET architecture. Thermal feedback regulates the charge current to limit the die temperature during high power operation or high ambient temperature. The charge
voltage is fixed at 4.2V, and the charge current can be programmed externally with a single resistor. The LTC4054 automatically terminates the charge cycle when the charge current drops to 1/10th the programmed
value after the final float voltage is reached. When the input supply (wall adapter or USB supply) is removed,
the LTC4054 automatically enetrs a low current state,dropping the battery drain current to less than 2μA. The
LTC4054 can be put into shudtown mode, reducing he supply current to 25μA.Other features include charge
current monitor, undervoltage lockout, automatic recharge and a status pin to indicate charge termination
and the presence of an input voltage.

Features
Programmable Charge Current Up to 800mA
No MOSFET, Sense Resistor or Blocking Diode Required
Complete Linear Charger in ThinSOT Package for
Single Cell Lithium-ion Batteries
Constant-Current/Constant-Voltage Operation with Thermal Regulation to Maximize Charge
    Rate Without Risk of Overheating
Charges Single Cell Li-Ion Batteries Directly from USB Port
Preset 4.2V Charge Voltage with ± 1% Accuracy
Charge Current Monitor Output for Gas Gauging
Automatic Recharge
Soft-Start Limits Inrush Current
Available in 5-Lead SOT-23 Package
2.9V Trickle Charge Threshold
C/10 Charge Termination
25mA Supply Current in Shutdown
2.9V Trickle Charge Threshold
Applications
Portable Media Players/MP3 players
Cellular and Smart mobile phone
Charging Docks and Cradles
Bluetooth Applications