Linear Li-Ion Battery
Charger with Thermal
Regulation in ThinSOT
s Programmable Charge Current up to 800mA
s No External MOSFET, Sense Resistor or Blocking
s Constant-Current/Constant-Voltage Operation with
Thermal Regulation Maximizes Charge Rate
Without Risk of Overheating*
s Charges Single Cell Li-Ion Batteries Directly from
s Preset 4.2V Charge Voltage with ±1% Accuracy
s Current Monitor Pin for Charge Termination
s 25µA Supply Current in Shutdown Mode
s Low Battery Charge Conditioning (Trickle Charging)
s Soft-Start Limits Inrush Current
s Available in a Low Profile (1mm) SOT-23 Package
s Wireless PDAs
s Cellular Phones
s Portable Electronics
, LTC and LT are registered trademarks of Linear Technology Corporation.
ThinSOT is a trademark of Linear Technology Corporation.
*U.S. Patent No. 6522118
The LTC®4057 is a constant-current/constant-voltage lin-
ear charger for single-cell lithium-ion batteries. Its
ThinSOTTM package and low external component count
make the LTC4057 especially well suited for portable
applications. Furthermore, the LTC4057 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 prevents overheating by regulating the
charge current to limit the die temperature during high
power operation or high ambient temperature conditions.
The charge voltage is preset at 4.2V and the charge current
can be programmed externally with a single resistor.
When the input supply (wall adapter or USB supply) is
removed, the LTC4057 automatically enters a low current
state, dropping the battery drain current to less than 2µA.
With power applied, the LTC4057 can be put into shut-
down mode, reducing the supply current to 25µA.
For the standalone version (on-board charge termination)
of the LTC4057, refer to the LTC4054.
1 SHDN PROG 5
Charge Curve (750mAh Battery)
VCC = 5V
θJA = 130°C/W
RPROG = 1.65kΩ
TA = 25°C
0 0.25 0.5 0.75 1.0 1.25 1.5 1.75 2.0 2.25