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LTC4080X

500mA Standalone Li-Ion Charger with Integrated 300mA Synchronous Buck in 3mm × 3mm DFN

Linear Technology 

LTC4080X

FEATURES

500mA Standalone Li-Ion

Charger with Integrated 300mA

Synchronous Buck in 3mm × 3mm DFN

DESCRIPTIO

■ Complete Linear Battery Charger with Integrated

Buck Converter in 3mm x 3mm DFN Package

Battery Charger:

■ Constant-Current/Constant-Voltage Operation

with Thermal Feedback to Maximize Charge Rate

Without Risk of Overheating

■ Internal 4.5 Hour Safety Timer for Termination

■ Charge Current Programmable Up to 500mA with

5% Accuracy

■ C/10 Charge Current Detection Output

■ 5µA Supply Current in Shutdown Mode

Switching Regulator:

■ High Efficiency Synchronous Buck Converter

■ 300mA Output Current (Constant-Frequency Mode)

■ 2.7V to 4.5V Input Range (Powered from BAT Pin)

■ 0.8V to VBAT Output Range

■ MODE Pin Selects Fixed (2.25MHz) Constant-Frequency

PWM Mode or Low ICC (23µA) Burst Mode®

Operation

■ 2µA BAT Current in Shutdown Mode

U

APPLICATIO S

■ Wireless Headsets

■ Bluetooth Applications

■ Portable MP3 Players

■ Multifunction Wristwatches

The LTC4080X is a complete constant-current/constant-

voltage linear battery charger for a single-cell 4.2V

lithium-ion/polymer battery with an integrated 300mA

synchronous buck converter. A 3mm × 3mm DFN package

and low external component count make the LTC4080X

especially suitable for portable applications. Furthermore,

the LTC4080X is specifically designed to work within USB

power specifications.

The ⎯C⎯H⎯R⎯G pin indicates when charge current has

dropped to ten percent of its programmed value (C/10).

An internal 4.5 hour timer terminates the charge cycle.

The full-featured LTC4080X battery charger also includes

automatic recharge and soft-start to limit inrush current.

If trickle charging is desired, please see the LTC4080

datasheet.

The LTC4080X integrates a synchronous buck converter

that is powered from the BAT pin. It has an adjustable

output voltage and can deliver up to 300mA of load cur-

rent. The buck converter also features low-current high-

efficiency Burst Mode operation that can be selected by

the MODE pin.

The LTC4080X is available in 10-lead, low profile (0.75 mm)

3mm × 3mm DFN and 10-lead MSE packages.

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

Burst Mode is a registered trademark of Linear Technology Corporation. All other

trademarks are the property of their respective owners. Protected by U.S. Patents,

including 6522118.

TYPICAL APPLICATIO

Li-Ion Battery Charger with 1.8V Buck Regulator

VCC

(3.75V

to 5.5V)

4.7µF

VCC

BAT

LTC4080X

EN_CHRG

SW

EN_BUCK

FB

MODE GND PROG

1OµH

500mA

+

4.7µF

4.2V

Li-Ion/

POLYMER

BATTERY

10pF 1M

806Ω

806k

VOUT

(1.8V/300mA)

COUT

4.7µF

4080X TA01a

Buck Efficiency vs Load Current

(VOUT = 1.8V)

100

1000

EFFICIENCY

80 (Burst)

EFFICIENCY

(PWM)

60

100

POWER

LOSS 10

(PWM)

40

20

0

0.01

POWER LOSS

1

(Burst)

VBAT = 3.8V

VOUT = 1.8V

0.1

L = 10µH

C = 4.7µF

0.01

0.1

1

10 100 1000

LOAD CURRENT (mA)

4080X TA01b

4080Xf

1

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