LTC3547B

1

3547bfb

OUTPUT CURRENT (mA)

30

90

100

20

10

80

50

70

60

40

1

100

1000

3547b TA01b

0

1

0.1

0.01

0.001

10

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 polymer and USB powered applications. Supply

current is only 1μA in shutdown.

An internally set 2.25MHz switching frequency allows the

use of tiny surface mount inductors and capacitors. Inter-

nal soft-start reduces inrush current during start-up. All

outputs are internally compensated to work with ceramic

capacitors. The LTC3547B is available in a low profile

(0.75mm) 3mm × 2mm DFN package. The LTC3547B

is also available in a fixed output voltage configuration

selected via internal resistor dividers (see Table 2).

■

Cellular Telephones

■

Digital Still Cameras

■

Wireless and DSL Modems

■

Portable Media Players

■

PDAs/Palmtop PCs

■

High Efficiency (Up to 96%) Dual Step-Down

Outputs

■

■

2.25MHz Constant-Frequency Operation

■

2.5V to 5.5V Input Voltage Range

■

Low Dropout Operation: 100% Duty Cycle

■

No Schottky Diodes Required

■

Internally Compensated for All Ceramic Capacitors

■

Independent Internal Soft-Start for Each Channel

■

Available in Fixed Output Versions

■

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

LTC3547B

SW2

SW1

10pF

10pF

GND

2.5V TO 5.5V

1.8V AT

300mA

2.5V AT

300mA

3547b TA01

237k

150k

475k

4.7μH

4.7μH

475k

4.7μF

4.7μF

4.7μF

Efficiency vs Output Current