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LTC3563

500mA, Synchronous Step-Down DC/DC Converter with Selectable Output Voltage

Linear Technology 

LTC3563

500mA, Synchronous

Step-Down DC/DC Converter

with Selectable Output Voltage

FEATURES

DESCRIPTIO

■ High Efficiency: Up to 96%

■ Pin Selectable Output Voltage: 1.28V/1.87V

■ Low Ripple (<20mVP-P) Burst Mode® Operation:

IQ = 26µA

■ Very Low Quiescent Current: Only 26µA

■ 2.5V to 5.5V Input Voltage Range

■ 2.25MHz Constant Frequency Operation

■ Low Dropout Operation: 100% Duty Cycle

■ No Schottky Diode Required

■ Internal Soft-Start Limits Inrush Current

■ Shutdown Mode Draws <1µA Supply Current

■ ±2% Output Voltage Accuracy

■ Current Mode Operation for Excellent Line and Load

Transient Response

■ Overtemperature Protected

■ Available in 2mm × 2mm 6-Lead DFN

U

APPLICATIO S

■ Cellular Telephones

■ Wireless and DSL Modems

■ Digital Cameras

■ MP3 Players

■ PDAs and Other Handheld Devices

The LTC®3563 is a high efficiency monolithic synchro-

nous buck converter using a constant frequency, current

mode architecture. A voltage select input allows the user

to program the output voltage to 1.28V or 1.87V. Supply

current during operation is only 26µA, dropping to <1µA in

shutdown. The 2.5V to 5.5V input voltage range makes the

LTC3563 ideally suited for single Li-Ion battery-powered

applications. 100% duty cycle provides low dropout opera-

tion, extending battery life in portable systems. Internal

power switches are optimized to provide high efficiency

and eliminate the need for an external Schottky diode.

The switching frequency is internally set at 2.25MHz,

allowing the use of small surface mount inductors and

capacitors. The LTC3563 is specifically designed to work

well with ceramic output capacitors, achieving very low

output voltage ripple and a small PCB footprint.

The LTC3563 is configured for the power saving Burst

Mode Operation.

, LTC, LT, LTM and Burst Mode are registered trademarks of Linear Technology

Corporation. All other trademarks are the property of their respective owners.

Protected by U.S. Patents, including 5481178, 6580258, 6304066, 6127815, 6498466,

6611131, 5994885.

TYPICAL APPLICATIO

VIN

2.7V TO 5.5V

CIN

10µF

CER

1.28V 1.87V

VIN

SW

LTC3563

RUN VOUT

VSEL

GND

2.2µH

VOUT

1.28V/1.87V

500mA

COUT

10µF

CER

3563 TA01a

Efficiency and Power Loss vs Output Current

100

90

80

70

60

50

40

30

20

10

0

0.1

1000

100

10

1

VIN = 3.6V

VOUT = 1.87V

0.1

1

10

100

1000

OUTPUT CURRENT (mA)

3563 TA01b

3563f

1

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