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LT1935

1.2MHz Boost DC/DC Converter in ThinSOT with 2A Switch

Linear Integrated System 

LT1935

1.2MHz Boost DC/DC

Converter in ThinSOT

with 2A Switch

FEATURES

■ 1.2MHz Switching Frequency

■ High Output Voltage: Up to 38V

■ Wide Input Range: 2.3V to 16V

■ Low VCESAT Switch: 180mV at 2A

■ Soft-Start

■ Uses Small Surface Mount Components

■ 5V at 1A from 3.3V Input

■ 12V at 600mA from 5V Input

■ Low Shutdown Current: < 1µA

■ Pin-for-Pin Compatible with the LT1613 and LT1930

■ Low Profile (1mm) SOT-23 (ThinSOTTM) Package

U

APPLICATIO S

■ Digital Cameras

■ Battery Backup

■ LCD Bias

■ Local 5V or 12V Supply

■ PC Cards

■ xDSL Power Supply

■ TFT-LCD Bias Supply

DESCRIPTIO

The LT®1935 is the industry’s highest power SOT-23

switching regulator. Its unprecedented 2A, 40V internal

switch allows high output currents to be generated in a

small footprint. Intended for space-conscious applica-

tions, the LT1935 switches at 1.2MHz, allowing the use of

tiny, low profile inductors and capacitors 2mm or less in

height. The NPN switch achieves a VCESAT of just 180mV

at 2A independent of supply voltage, resulting in high

efficiency even at maximum power levels from a 3V input.

A constant frequency, internally compensated, current

mode PWM architecture results in low, predictable output

noise that is easy to filter. Low ESR ceramic capacitors can

be used on the output, further reducing noise to the

millivolt level. The high voltage switch on the LT1935 is

rated at 40V, making the device ideal for boost converters

up to 38V as well as for single-ended primary inductance

converter (SEPIC) and flyback designs. The device can

generate 5V at up to 1A from a 3.3V supply or 5V at 550mA

from four alkaline cells in a SEPIC design.

The LT1935 is available in a 5-lead SOT-23 package.

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

ThinSOT is a trademark of Linear Technology Corporation.

TYPICAL APPLICATIO

L1

VIN

4.2µH

D1

5V

4.7µF

ON OFF

VIN

SW

LT1935

SHDN

FB

GND

84.5k

10k

VOUT

12V

600mA

10µF

D1: ON SEMI MBRM120

L1: SUMIDA CDRH5D28-4R2

1935 F01

Figure 1. 5V to 12V, 600mA Step-Up DC/DC Converter

Efficiency, VOUT = 12V

90

85

VIN = 5V

80

VIN = 3.3V

75

70

65

60

55

50

0 100 200 300 400 500 600 700

LOAD CURRENT (mA)

1935 F01b

1935f

1

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