LTC3547BEDDB Ver la hoja de datos (PDF) - Linear Technology

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LTC3547BEDDB

Dual Monolithic 300mA Synchronous Step-Down Regulator

Linear Technology 

FEATURES

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

Outputs

■ 300mA Output Current per Channel at VIN = 3V

■ 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

■ Ultralow Shutdown Current: IQ < 1μA

■ Low Profile (0.75mm) 8-Lead 3mm × 2mm

DFN Package

U

APPLICATIO S

■ Cellular Telephones

■ Digital Still Cameras

■ Wireless and DSL Modems

■ Portable Media Players

■ PDAs/Palmtop PCs

LTC3547B

Dual Monolithic

300mA Synchronous

Step-Down Regulator

DESCRIPTIO

The LTC®3547B is a dual, 2.25MHz, constant-frequency,

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).

, 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.

TYPICAL APPLICATIO

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

VIN

2.5V TO 5.5V

VOUT2

1.8V AT

300mA

4.7μF

4.7μH

10pF

RUN2 VIN RUN1

LTC3547B

SW2

SW1

4.7μH

10pF

VOUT1

2.5V AT

300mA

4.7μF 475k

VFB2

VFB1

GND

237k

150k 475k

4.7μF

3547b TA01

100

90

80

70

60

50

40

30

20

10

0

1

Efficiency vs Output Current

for VOUT = 2.5V

1

0.1

0.01

VIN = 2.7V

VIN = 3.6V

VIN = 4.2V

0.001

10

100

1000

OUTPUT CURRENT (mA)

3547b TA01b

3547bfb

1

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