LTC3544B

1

3544bfa

TYPICAL APPLICATION

FEATURES

APPLICATIONS

DESCRIPTION

Quad Synchronous

Step-Down Regulator: 2.25MHz,

300mA, 200mA, 200mA, 100mA

The LTC

synchronous buck regulator using a constant frequency,

current mode architecture. The four regulators operate in-

dependently with separate run pins. The 2.25V to 5.5V input

voltage range makes the LTC3544B well suited for single

Li-Ion/polymer battery-powered applications. 100% duty

cycle provides low dropout operation, extending battery

runtime in portable systems. At moderate and low output

load levels PWM pulse skip mode operation provides very

low output ripple voltage for noise sensitive applications.

Switching frequency is internally set to 2.25MHz, al-

lowing the use of small surface mount inductors and

capacitors.

The internal synchronous switches increase efficiency

and eliminate the need for external Schottky diodes. Low

output voltages are easily supported with the 0.8V feedback

reference voltage.

The LTC3544B is available in a low profile (0.75mm) (3mm

× 3mm) QFN package.

■

High Efficiency: Up to 95%

■

Four Independent Regulators Provide Up to 300mA,

200mA, 200mA and 100mA Output Current

■

2.25V to 5.5V Input Voltage Range

■

2.25MHz Constant Frequency Operation

■

No Schottky Diodes Required

■

Low Dropout Operation: 100% Duty Cycle

■

Pulse Skipping at Low Load for Minimum Ripple

■

0.8V Reference Allows Low Output Voltages

■

Shutdown Mode Draws <1μA Supply Current

■

Current Mode Operation for Excellent Line and Load

Transient Response

■

Overtemperature Protected

■

Low Profile (3mm × 3mm) 16-Lead QFN Package

■

Cellular Telephones

■

Personal Information Appliances

■

Wireless and DSL Modems

■

Digital Still Cameras

■

Media Players

■

Portable Instruments

, LT, LTC and LTM 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.

4.7

μH

3.3

μH

10

μH

93.1k

107k

4.7

μF

CER

4.7

μF

CER

3.3

μH

133k

59k

107k

118k

3544B TA01a

4.7

μF

CER

4.7

μF

CER

4.7

μF

CER

0.8V

1.2V

1.5V

2.25V TO 5.5V

1.8V

RUN200B

SW200B

RUN200A

SW200A

RUN300

SW300

RUN100

SW100

LTC3544B

GNDA

PGND

100k

High Efficiency Quad Step-Down Converter

LOAD CURRENT (A)

30

90

100

20

10

80

50

70

60

40

0.0001

0.01

0.1

1

3544B TA01b

0

1

0.1

0.01

0.001

0.001

EFFICIENCY

POWER LOSS

Efficiency vs Load Current, 300mA

Channel, All Other Channels Off