LTC3444 データシートの表示（PDF） - Linear Technology

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LTC3444

Micropower Synchronous Buck-Boost DC/DC Converter for WCDMA Applications

Linear Technology 

LTC3444

Micropower Synchronous

Buck-Boost DC/DC Converter

for WCDMA Applications

FEATURES

■ Optimized Features for WCDMA Handsets

■ Regulated Output with Input Voltages

Above, Below, or Equal to the Output

■ 0.5V to 5V Output Range

■ Up to 400mA Continuous Output Current From

a Single Lithium-Ion Cell

■ Minimal External Components

■ 1.5MHz Fixed Frequency Operation

■ Internal Loop Compensation for Fast Response

<25μs Full Scale Output Slewing; COUT 4.7μF

■ Output Disconnect in Shutdown

■ 2.75V to 5.5V Input

■ <1μA Shutdown Current

■ Internal Soft-Start

■ Output Overvoltage Protection

■ Single Inductor, No Schottky Diodes Required

■ Small, Thermally Enhanced 8-Lead (3mm × 3mm)

DFN Package

U

APPLICATIO S

■ WCDMA Applications–3G Handsets with High Speed

Data Rate Capability

■ MP3 Players

■ Digital Cameras

DESCRIPTIO

The LTC®3444 is a highly efficient, fixed frequency, buck-

boost DC/DC converter, which operates from input volt-

ages above, below, and equal to the output voltage. The

topology incorporated in the IC provides a continuous

transfer function through all operating modes, making the

product ideal for a single Lithium-Ion or multi-cell

applications where the output voltage can vary over a wide

range.

The LTC3444 has been optimized for use in 3G WCDMA

applications. A unique design yields high efficiency at

very low output voltages while also eliminating external

components. The high speed error amplifier provides the

fast transient response required to slew the RF power

amplifier from standby to transmit and transmit to stand

by power levels. Output overvoltage protection protects

the RF power amplifier.

Operating frequency is internally set to 1.5MHz to mini-

mize external component size while maximizing efficiency.

Other features include <1μA shutdown current, internal

soft-start, peak current limit and thermal shutdown. The

LTC3444 is available in a small, thermally enhanced

8-lead (3mm × 3mm) DFN package.

, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.

All other trademarks are the property of their respective owners.

Protected by U.S. Patents including 6404251, 6166527.

TYPICAL APPLICATIO

2.2μH

3.1V TO 4.2V

4.7μF

+

Li-Ion

LTC3444

SW1

SW2

VIN

SHDN

VOUT

FB

GND

VC

DAC

340k

VOUT

0.8V TO 4.2V

4.7μF

205k

267k

VCONTROL

3444 TA01

LTC3444 Dynamic Response

VOUT

VCONTROL

10μs/DIV

VIN = 3.6V, VOUT = 0.8V TO 4.2V

VCONTROL = 2.36V TO 0.28V, ILOAD = 100mA

3444 G16a

3444fb

1

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