LTC3547

1

3547fa

OUTPUT CURRENT (mA)

30

90

100

20

10

80

50

70

60

40

0.1

10

100

1000

3547 TA01b

0

1

0.1

0.01

0.001

0.0001

1

Dual Monolithic

300mA Synchronous

Step-Down Regulator

synchronous step-down DC/DC converter in a tiny 3mm

× 2mm DFN package. 100% duty cycle provides low drop-

out operation, extending battery life in portable systems.

Low output voltages are supported with the 0.6V feed-

back reference voltage. Each regulator can supply 300mA

continuous output current.

The input voltage range is 2.5V to 5.5V, making it ideal for

Li-Ion and USB powered applications. Supply current dur-

ing operation is only 40µA and drops to < 1µA in shutdown.

light loads, further extending battery life.

An internally set 2.25MHz switching frequency allows

the use of tiny surface mount inductors and capacitors.

Internal soft-start reduces inrush current during start-

up. All outputs are internally compensated to work with

ceramic capacitors. The LTC3547 is available in a low

profile (0.75mm) 3mm × 2mm DFN package. The LTC3547

is also available in a fixed output voltage configuration,

eliminating the need for the external feedback networks

(see Table 2).

■

Cellular Telephones

■

Digital Still Cameras

■

Wireless and DSL Modems

■

PDAs/Palmtop PCs

■

Portable Media Players

■

High Efficiency Dual Step-Down Outputs: Up to 96%

■

■

Automatic Low Ripple Burst Mode Operation

■

Only 40µA Quiescent Current During Operation

(Both Channels)

■

2.25MHz Constant-Frequency Operation

■

2.5V to 5.5V Input Voltage Range

■

Low Dropout Operation: 100% Duty Cycle

■

Internally Compensated for All Ceramic Capacitors

■

Independent Internal Soft-Start for Each Channel

■

Current Mode Operation for Excellent Line and Load

Transient Response

■

0.6V Reference Allows Low Output Voltages

■

Short-Circuit Protected

■

■

Low Profile (0.75mm) 8-Lead 3mm × 2mm

DFN Package

Dual Monolithic Buck Regulator in 8-Lead 3mm × 2mm DFN

APPLICATIO S

FEATURES

DESCRIPTIO

TYPICAL APPLICATIO

, 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 6580258, 5481178, 6304066, 6127815, 6498466, 6611131.

RUN2

RUN1

LTC3547

SW2

SW1

10pF

10pF

GND

2.5V TO 5.5V

1.8V AT

300mA

2.5V AT

300mA

3547 TA01

237k

150k

475k

L2

4.7

µH

L1

4.7

µH

475k

4.7

µF

4.7

µF

4.7

µF

Efficiency vs Output Current