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LTC3544EUD-TRPBF

Quad Synchronous Step-Down Regulator: 2.25MHz, 300mA, 200mA, 200mA, 100mA

Linear Technology 

LTC3544

Quad Synchronous

Step-Down Regulator: 2.25MHz,

300mA, 200mA, 200mA, 100mA

FEATURES

■ 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

■ Extremely Low Channel-to-Channel Transient

Crosstalk

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

IQ = 70μA (All Channels On)

■ 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

APPLICATIONS

■ Cellular Telephones

■ Personal Information Appliances

■ Wireless and DSL Modems

■ Digital Still Cameras

■ Media Players

■ Portable Instruments

DESCRIPTION

The LTC®3544 is a quad, high efficiency, monolithic

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

Burst Mode® operation increases efficiency at light loads,

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.

, 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.

TYPICAL APPLICATION

High Efficiency Quad Step-Down Converter

VIN

2.25V TO 5.5V

VOUT2

1.5V

200mA

4.7μF

CER

4.7μF

CER

4.7μH

93.1k

107k

VOUT4

1.8V

300mA

4.7μF

CER

3.3μH

133k

107k

VCC

RUN200B

SW200B

VFB200B

PVIN

RUN200A

SW200A

VFB200A

LTC3544

RUN300

SW300

VFB300

GNDA

RUN100

SW100

VFB100

PGND

3.3μH

100k

VOUT3

0.8V

200mA

4.7μF

CER

10μH

59k

118k

VOUT1

1.2V

100mA

4.7μF

CER

3544B TA01a

Efficiency vs Load Current, 300mA

Channel, All Other Channels Off

100

1

90

80

EFFICIENCY

0.1

70

60

LOSS

50 VOUT = 2.5V

0.01

40 TA = 25°C

30

20

10

0

0.0001

0.001

0.001

0.01

VIN = 2.7V

VIN = 3.6V

VIN = 4.2V 0.0001

0.1

1

LOAD CURRENT (A)

3544 TA01b

3544fa

1

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