LT3475/LT3475-1

1

3475fb

Dual Step-Down

1.5A LED Driver

converters designed to operate as a constant-current

source. An internal sense resistor monitors the output

current allowing accurate current regulation ideal for

driving high current LEDs. The high side current sense al-

lows grounded cathode LED operation. High output current

accuracy is maintained over a wide current range, from

50mA to 1.5A, allowing a wide dimming range. Unique

PWM circuitry allows a dimming range of 3000:1, avoid-

ing 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 20 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 its wide input range of 4V to 36V, the LT3475/LT3475-1

regulate a broad array of power sources. 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

■

3000:1 Dimming Range

■

Wide Input Range: 4V to 36V Operating, 40V

Maximum

■

Accurate and Adjustable Control of LED Current

from 50mA to 1.5A

■

High Side Current Sense Allows Grounded Cathode

LED Operation

■

Open LED (LT3475) and Short Circuit Protection

■

LT3475-1 Drives LED Strings Up to 25V

■

Accurate and Adjustable 200kHz to 2MHz

Switching Frequency

■

Anti-Phase Switching Reduces Ripple

■

Uses Small Inductors and Ceramic Capacitors

■

Available in the Compact 20-Lead TSSOP Thermally

Enhanced Surface Mount Package

Dual Step-Down 1.5A LED Driver

APPLICATIO S

FEATURES

DESCRIPTIO

TYPICAL APPLICATIO

Efficiency

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

All other trademarks are the property of their respective owners. Patents Pending.

BOOST1

BOOST2

SW1

SW2

OUT1

OUT2

LED1

LED2

PWM1

PWM2

REF

GND

LT3475

5V TO 36V

SHDN

0.22μF

4.7μF

10μH

10μH

0.22μF

24.3k

2.2μF

2.2μF

DIMMING*

CONTROL

*DIMMING

CONTROL

0.1μF

0.1μF

3475 TA01

1.5A LED

CURRENT

1.5A LED

CURRENT

*SEE APPLICATIONS SECTION FOR DETAILS

LED CURRENT (A)

0

70

75

80

3475 TA01b

65

60

55

0.5

1

85

90

95

1.5

TWO SERIES CONNECTED

WHITE 1.5A LEDS

SINGLE WHITE 1.5A LED