The LT3475/LT3475-1 are dual step-down 1.5A LED drivers. They are 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 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.
The LT3475/LT3475-1 is a dual step‑down DC/DC converter designed as a constant‑current LED driver with a wide input range (4 V‑36 V) and output current capability from 50 mA to 1.5 A. It features True Color PWM dimming, high‑frequency operation (200 kHz‑2 MHz), and built‑in protections such as open‑circuit, short‑circuit, UVLO and thermal shutdown.
This manual includes the device’s features, absolute maximum ratings, pin configuration, electrical characteristics, typical performance graphs, pin functions, block diagram, operation description, application information, switching‑frequency programming, package details, a typical application circuit, and a list of related parts.
| Input Voltage Range | 4 V to 36 V |
|---|---|
| Output Current Range | 50 mA to 1.5 A |
| Switching Frequency Range | 200 kHz to 2 MHz |
| Package Type | 20‑lead Plastic TSSOP |
| Maximum Duty Cycle | 95 % |
| LED Pin Current (max) | 1.5 A |
The device operates from 4 V up to 36 V input.
Connect a resistor from the Ry pin to ground; the frequency can be programmed between 200 kHz and 2 MHz.
The device is supplied in a 20‑lead Plastic TSSOP package.