The CST4084 is a complete constant-current/constant-voltage linear charger for single cell lithium-ion batteries. 

    Its SOT package and low external component count make the CST4084 ideally suited for portable applications. Furthermore, the CST4084 is specifically designed to work within USB power specifications.No external sense resistor is needed, and no blocking diode 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 CST4084 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 CST4084 automatically enters a low current state, dropping the battery drain current to less than 1μA.

    The CST4084 can be put into shutdown mode, reducing the supply current to 35μA. 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.

CST4084 Features:

Constant-Current/Constant-Voltage Operation with Thermal Regulation to Maximize Charge Rate Without Risk of Overheating 

No MOSFET, Sense Resistor or Blocking Diode Required 

Complete Linear Charger in SOT Package for Single Cell Lithium-Ion Batteries 

Charges Single Cell Li-Ion Batteries Directly from USB Port 

Charge Current Monitor Output for Gas Gauging

Programmable Charge Current Up to 800mA 

Charge Status Output Pin 

C/10 Charge Termination 

Automatic Recharge 

Preset 4.2V Charge Voltage with ±1% Accuracy 

35µA Supply Current in Shutdown 

2.9V Trickle Charge Threshold 

Soft-Start Limits Inrush Current 

Available in 5-Lead SOT-23 Package 

RoHS Compliant and Lead (Pb) Free

Cellular Telephones 

Charging Docks and Cradles

Bluetooth Application 

Wearable Application