LTC3544

1

3544fa

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Cellular Telephones

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Personal Information Appliances

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Wireless and DSL Modems

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Digital Still Cameras

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Media Players

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Portable Instruments

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

independently with separate run pins. The 2.25V to 5.5V

input voltage range makes the LTC3544 well suited for

single Li-Ion/polymer battery-powered applications.

100% duty cycle provides low dropout operation, ex-

tending battery runtime in portable systems. Low ripple

further extending battery runtime with typically only 20mV

of ripple.

Switching frequency is internally set to 2.25MHz, allowing

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 LTC3544 is available in a low profile (0.75mm) (3mm

× 3mm) QFN package.

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High Efficiency: Up to 95%

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Four Independent Regulators Provide Up to 300mA,

200mA, 200mA and 100mA Output Current

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2.25V to 5.5V Input Voltage Range

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2.25MHz Constant-Frequency Operation

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No Schottky Diodes Required

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Extremely Low Channel-to-Channel Transient

Crosstalk

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0.8V Reference Allows Low Output Voltages

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Shutdown Mode Draws <1μA Supply Current

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Current Mode Operation for Excellent Line and Load

Transient Response

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Overtemperature Protected

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

, 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 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

200mA

1.2V

100mA

1.5V

200mA

2.25V TO 5.5V

1.8V

300mA

RUN200B

SW200B

RUN200A

SW200A

RUN300

SW300

RUN100

SW100

LTC3544

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

3544 TA01b

0

1

0.1

0.01

0.001

0.0001

0.001

EFFICIENCY

LOSS

Efficiency vs Load Current, 300mA

Channel, All Other Channels Off