LT3474IFE-TRPBF データシートの表示（PDF） - Linear Technology

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LT3474IFE-TRPBF

Step-Down 1A LED Driver

Linear Technology 

LT3474/LT3474-1

Step-Down

1A LED Driver

FEATURES

n True Color PWM™ Delivers Constant Color with

400:1 Dimming Range

n Wide Input Range: 4V to 36V

n Up to 1A LED Current

n Adjustable 200kHz–2MHz Switching Frequency

n Adjustable Control of LED Current

n Integrated Boost Diode

n High Output Current Accuracy is Maintained

Over a Wide Range from 35mA to 1A

n Open LED (LT3474) and Short-Circuit Protection

n High Side Sense Allows Grounded

Cathode Connection

n Uses Small Inductors and Ceramic Capacitors

n LT3474-1 Drives LED Strings Up to 26V

n Compact 16-Lead TSSOP Thermally Enhanced

Surface Mount Package

APPLICATIONS

■ Automotive and Avionic Lighting

■ Architectural Detail Lighting

■ Display Backlighting

■ Constant Current Sources

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

True Color PWM is a trademark of Linear Technology Corporation. All other trademarks are

the property of their respective owners. Patent Pending

DESCRIPTION

The LT®3474/LT3474-1 are fixed frequency step-down

DC/DC converters designed to operate as constant-current

sources. An internal sense resistor monitors the output

current allowing accurate current regulation, ideal for

driving high current LEDs. High output current accuracy

is maintained over a wide current range, from 35mA to

1A, allowing a wide dimming range.

Unique PWM circuitry allows a dimming range of 400:1,

avoiding the color shift normally associated with LED

current dimming.

The high switching frequency offers several advantages,

permitting the use of small inductors and ceramic capaci-

tors. Small inductors combined with the 16-lead TSSOP

surface mount package save space and cost versus

alternative solutions. The constant switching frequency

combined with low-impedance ceramic capacitors result

in low, predictable output ripple.

With their wide input range of 4V to 36V, the LT3474/

LT3474-1 regulate a broad array of power sources, from

5V logic rails to unregulated wall transformers, lead acid

batteries and distributed power supplies. A current mode

PWM architecture provides fast transient response and

cycle-by-cycle current limiting. Frequency foldback and

thermal shutdown provide additional protection.

TYPICAL APPLICATION

Step-Down 1A LED Driver

VIN

5V TO 36V

2.2μF

80.6k

0.1μF

VIN

BOOST

SHDN

SW

LT3474

RT

BIAS

REF

OUT

VADJ

PWM

VC

LED

GND

0.22μF

10μH

DIMMING*

CONTROL

LED1

2.2μF

*SEE APPLICATIONS SECTION FOR DETAILS

3474 TA01a

95

VIN = 12V

90

Efficiency

TWO SERIES CONNECTED

WHITE 1A LEDS

85

80

ONE WHITE 1A LED

75

70

65

60

55

0

200 400 600 800 1000

LED CURRENT (mA)

3474 G02

3474fd

1

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