Features

• True Color PWM Delivers Constant Color with 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

Typical Application

Description

The LT3475 is a dual step-down DC/DC converter 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 allows 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, 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 capacitors. Small inductors combined with the LT3475's 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 regulates 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.