Final Electrical Specifications
LTC4007
4A, High Efficiency,
Standalone Li Battery Charger
January 2003
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FEATURES
DESCRIPTION
The LTC®4007 is a complete constant-current/constant-
voltage charger controller for 3- or 4-cell lithium-ion
batteries.ThePWMcontrollerusesasynchronous,quasi-
constant frequency, constant off-time architecture that
will not generate audible noise even when using ceramic
capacitors. Charging current is programmable to ±5%
accuracyusingaprogrammingresistor.Chargingcurrent
can also be monitored as a voltage across the program-
ming resistor.
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Complete Charger Controller for 3- or 4-Cell
Lithium-Ion Batteries
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High Conversion Efficiency: Up to 96%
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Output Currents Exceeding 4A
±0.8% Charging Voltage Accuracy
Built-In Charge Termination for Li-Ion Batteries
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AC Adapter Current Limiting Maximizes Charge Rate*
Thermistor Input for Temperature Qualified Charging
Wide Input Voltage Range: 6V to 28V
0.5V Dropout Voltage; Maximum Duty Cycle: 98%
Programmable Charge Current: ±5% Accuracy
Indicator Outputs for Charging, C/10 Current
Detection, AC Adapter Present, Low Battery, Input
Current Limiting and Faults
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The output float voltage is pin programmed for cell count
(3 cells or 4 cells) and chemistry (4.2V/4.1V). A timer,
programmed by an external resistor, sets the total charge
time.Chargingisautomaticallyrestartedwhencellvoltage
falls below 3.9V/cell.
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Charging Current Monitor Output
Available in a 24-Pin Narrow SSOP Package
LTC4007 includes a thermistor input, which suspends
charging if an unsafe temperature condition is detected. If
the cell voltage is less than 2.5V, a low-battery indicator
asserts and can be used to program a trickle charge cur-
rent to safely charge depleted batteries. The FAULT pin is
also asserted and charging terminates if the low-battery
conditionpersistsformorethan1/4ofthetotalchargetime.
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APPLICATIO S
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Notebook Computers
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Portable Instruments
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Battery-Backup Systems
Standalone Li-Ion Chargers
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, LTC and LT are registered trademarks of Linear Technology Corporation.
*U.S. Patent No. 5,723,970
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TYPICAL APPLICATIO
12.6V, 4A Li-Ion Battery Charger
INPUT SWITCH
DCIN
0V TO 28V
0.1µF
4.9k
3C4C
DCIN
INFET
CLP
V
LOGIC
0.025Ω
15nF
100k
100k 100k
CHEM
LOBAT
SYSTEM
LOAD
LOBAT
I
I
LTC4007 CLN
TGATE
CL
CL
20µF
ACP
SHDN
FAULT
CHG
ACP
Q1
10µH
0.025Ω
SHDN
BGATE
Li-Ion
BATTERY
Q2
FAULT
CHG
PGND
CSP
20µF
3.01k
FLAG
FLAG
NTC
BAT
32.4k
3.01k
PROG
ITH
CHARGING
CURRENT
MONITOR
R
T
THERMISTOR
0.0047µF
0.47µF
GND
6.04k
0.12µF
10k
NTC
Q1: Si4431DY
Q2: FDC6459
TIMING RESISTOR
(~2 HOURS)
26.7k
309k
4007 TA01
4007i
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of its circuits as described herein will notinfringe onexisting patent rights.
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