■ Features
 Programmable charge current up to 500mA
 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 gaugin
 Charge status output pin
 C/10 charge termination
 25μA supply current in shutdown
 2.9V trickle charge threshold (XT2055)
 Soft-start limits inrush current
 Available in 6-Lead SOT-23
■ General Description
The XT2055 is a complete constant-current /constant
-voltage linear charger for single cell lithium-ion batteries.
Its Thin SOT package and low external component count
make the XT2055 ideally suited for portable applications.
Furthermore, the XT2055 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 XT2055 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 XT2055 automatically enters a low current
state, dropping the battery drain current to less than 2μA.
The XT2055 can be put into shutdown mode, reducing the
supply current to 25μA.
Other features include charge current monitor,
under-voltage lockout, automatic recharge and a status pin
to indicate charge termination and the presence of an input
voltage.
■ Applications
 Cellular Telephones, PDAs, MP3 Players
 Bluetooth Applications