LTC4078X Datasheet, PDF (1/16 Pages) Linear Technology – Dual Input Li-Ion Battery Charger with Overvoltage Protection

LTC4078X
Dual Input Li-Ion Battery
Charger with Overvoltage Protection
FEATURES
■ _{22V Maximum Voltage for Wall Adapter and}
USB Inputs
■ _{Charge Single-Cell Li-Ion Batteries from Wall}
Adapter and USB Inputs
■ _{Automatic Input Power Detection and Selection}
■ _{Charge Current Programmable Up to 950mA from}
Wall Adapter Input
■ _{Overvoltage Lockout for Wall Adapter and USB Inputs}
■ _{Battery Detection Input Disables Charger When No}
Battery is Present
■ _{No External MOSFET, Sense Resistor or Blocking}
Diode Needed
■ _{Thermal Regulation Maximizes Charge Rate Without}
Risk of Overheating*
■ _{Preset Charge Voltage with ±0.6% Accuracy}
■ _{Programmable Charge Current Termination}
■ _{40µA USB Suspend Current in Shutdown}
■ _{Charge Status Output}
■ _{Automatic Recharge}
■ _{No Trickle Charge}
■ _{Available in a Thermally Enhanced, Low Profile}
(0.75mm) 10-Lead (3mm × 3mm) DFN Package
APPLICATIONS
■ _{Cellular Telephones}
■ _{Handheld Computers}
■ _{Portable MP3 Players}
■ _{Digital Cameras}
DESCRIPTION
The LTC^®4078X is a standalone linear charger that is
capable of charging a single-cell Li-Ion/Polymer battery
from both wall adapter and USB inputs. The charger can
detect power at the inputs and automatically select the
appropriate power source for charging.
No external sense resistor or blocking diode is required
for charging due to the internal MOSFET architecture.
The LTC4078X features a maximum 22V rating for both
wall adapter and USB inputs, although charging stops if
the selected power source exceeds the overvoltage limit.
Internal thermal feedback regulates the battery charge
current to maintain a constant die temperature during high
power operation or high ambient temperature conditions.
The float voltage is fixed at 4.2V and the charge current
is programmed with an external resistor. The LTC4078X
terminates the charge cycle when the charge current drops
below the programmed termination threshold after the
final float voltage is reached.
Other features include battery present detection, automatic
recharge, undervoltage lockout, charge status outputs, and
“power present” status outputs to indicate the presence of
wall adapter or USB power. The device is offered in a low
profile (0.75mm) 3mm × 3mm 10-lead DFN package.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All
other trademarks are the property of their respective owners.
*Protected by U.S. Patents including 6522118, 6700364.
TYPICAL APPLICATION
High Voltage Dual Input Battery Charger
for Li-Ion Battery Pack
WALL
ADAPTER
USB
PORT
1µF
LTC4078X
DCIN
BAT
USBIN BATDET
1µF
IUSB
2k
1%
IDC
1.24k
ITERM
GND
1%
800mA (WALL)
500mA (USB)
+
3.9k
4.2V
Li-Ion
BATTERY
PACK
2k
1%
4078X TA01
Charger Current vs Supply Voltage
900
R_IDC = 1.24k
800
R_IUSB = 2k
V_BAT = 3.5V
700
V_BATDET = 0V
600
CHARGE FROM DCIN
500
400
CHARGE
300
FROM USBIN
200
100
0
2 3 4 5 6 7 8 19 20
SUPPLY VOLTAGE (V)
4078x TA01b
4078xf
1