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LTC4007

4007i

4A, High Efficiency,

Standalone Li Battery Charger

January 2003

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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

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±0.8% Charging Voltage Accuracy

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Built-In Charge Termination for Li-Ion Batteries

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AC Adapter Current Limiting Maximizes Charge Rate*

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Thermistor Input for Temperature Qualified Charging

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Wide Input Voltage Range: 6V to 28V

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0.5V Dropout Voltage; Maximum Duty Cycle: 98%

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Programmable Charge Current:

±5% Accuracy

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Indicator Outputs for Charging, C/10 Current

Detection, AC Adapter Present, Low Battery, Input

Current Limiting and Faults

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Charging Current Monitor Output

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Available in a 24-Pin Narrow SSOP Package

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Notebook Computers

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Portable Instruments

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Battery-Backup Systems

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Standalone Li-Ion Chargers

, LTC and LT are registered trademarks of Linear Technology Corporation.

FEATURES

APPLICATIO S

Final Electrical Specifications

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 not infringe on existing patent rights.

TYPICAL APPLICATIO

12.6V, 4A Li-Ion Battery Charger

The LTC

voltage charger controller for 3- or 4-cell lithium-ion

batteries. The PWM controller uses a synchronous, quasi-

constant frequency, constant off-time architecture that

will not generate audible noise even when using ceramic

capacitors. Charging current is programmable to

±5%

accuracy using a programming resistor. Charging current

can also be monitored as a voltage across the program-

ming resistor.

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. Charging is automatically restarted when cell voltage

falls below 3.9V/cell.

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

condition persists for more than 1/4 of the total charge time.

3C4C

CHEM

LOBAT

ACP

SHDN

FAULT

CHG

FLAG

NTC

LOBAT

ACP

SHDN

FAULT

CHG

FLAG

DCIN

INFET

CLP

CLN

TGATE

BGATE

PGND

CSP

BAT

PROG

ITH

GND

LTC4007

32.4k

309k

0.47

µF

THERMISTOR

10k

NTC

TIMING RESISTOR

(~2 HOURS)

100k

100k

100k

DCIN

0V TO 28V

0.1

µF

INPUT SWITCH

15nF

Q1

Q2

20

µF

10

µH

4.9k

3.01k

3.01k

0.025

Ω

0.025

Ω

20

µF

Li-Ion

BATTERY

CHARGING

CURRENT

MONITOR

Q1: Si4431DY

Q2: FDC6459

SYSTEM

LOAD

0.12

µF

6.04k

26.7k

0.0047

µF

4007 TA01

*U.S. Patent No. 5,723,970