LTC4068-4.2/LTC4068X-4.2
Standalone Linear
Li-Ion Battery Charger with
Programmable Termination
FEATURES
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DESCRIPTIO
Programmable Charge Current Up to 950mA
Complete Linear Charger in DFN Package
No MOSFET, Sense Resistor or Blocking Diode
Required
Thermal Regulation Maximizes Charge Rate
Without Risk of Overheating*
Charges Directly from a USB Port
Programmable Charge Current Termination
Preset 4.2V Charge Voltage with
±1%
Accuracy
Charge Current Monitor Output for Gas Gauging*
Automatic Recharge
Charge Status Output
“AC Present” Output
2.9V Trickle Charge Threshold (LTC4068)
Available Without Trickle Charge (LTC4068X)
Soft-Start Limits Inrush Current
Low Profile (3mm
×
3mm
×
0.75mm) DFN Package
The LTC
®
4068 is a complete constant-current/constant-
voltage linear charger for single cell lithium-ion batteries.
Its DFN package and low external component count make
the LTC4068 ideally suited for portable applications. Fur-
thermore, the LTC4068 is designed to work within USB
power specifications.
No external sense resistor or external blocking diode are
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 conditions. The charge voltage is fixed at
4.2V and the charge current is programmed with a resis-
tor. The LTC4068 terminates the charge cycle when the
charge current drops below the programmed termination
threshold after the final float voltage is reached.
When the input supply (wall adapter or USB supply) is
removed, the LTC4068 enters a low current state dropping
the battery drain current to less than 2µA. Other features
include charge current monitor, undervoltage lockout,
automatic recharge and status pins to indicate charge
termination and the presence of adequate input voltage.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Protected by U.S. Patents, including 6522118.
APPLICATIO S
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Cellular Telephones, PDAs, MP3 Players
Bluetooth Applications
TYPICAL APPLICATIO
Complete Charge Cycle (750mAh Battery)
700
Single Cell Li-Ion Battery Charger with C/5 Termination
CHARGE CURRENT (mA)
600
500
400
300
200
100
CONSTANT
CURRENT
CONSTANT
VOLTAGE
600mA
V
IN
4.5V TO 6.5V
V
CC
BAT
LTC4068-4.2
CHRG
ACPR ITERM
EN
PROG
GND
+
825Ω
1.65k
1-CELL
Li-Ion
BATTERY
1µF
406842 TA01
0
3.00
0 0.25 0.5 0.75 1.0 1.25 1.5 1.75 2.0 2.25
406842 TA02
TIME (HOURS)
406842fa
V
CC
= 5V
θ
JA
= 40°C/W
R
PROG
= 1.65k
R
TERM
= 825Ω
T
A
= 25°C
U
4.75
4.50
BATTERY VOLTAGE (V)
U
U
4.25
4.00
3.75
3.50
3.25
1
LINER [ LINEAR TECHNOLOGY ]
