LT3474/LT3474-1

1

3474fd

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.

■

Automotive and Avionic Lighting

■

Architectural Detail Lighting

■

Display Backlighting

■

Constant Current Sources

400:1 Dimming Range

Over a Wide Range from 35mA to 1A

Cathode Connection

Surface Mount Package

TYPICAL APPLICATION

DESCRIPTION

Step-Down

1A LED Driver

Step-Down 1A LED Driver

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

FEATURES

APPLICATIONS

Efficiency

BIAS

OUT

PWM

LED

LED1

DIMMING*

CONTROL

LT3474

0.1μF

5V TO 36V

2.2μF

0.22μF

10μH

3474 TA01a

80.6k

*SEE APPLICATIONS SECTION FOR DETAILS

SHDN

REF

BOOST

SW

GND

2.2μF

LED CURRENT (mA)

0

70

75

80

600

1000

3474 G02

65

60

55

200

400

800

85

90

95

TWO SERIES CONNECTED

WHITE 1A LEDS

ONE WHITE 1A LED