Features and Benefits
- 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
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.
- Automotive and Avionic Lighting
- Architectural Detail Lighting
- Display Backlighting
- Constant-Current Sources
Product Lifecycle Production
At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.
Evaluation Kits (2)
Demonstration circuit 1315 features the LT3475-1 dual step-down 1.5A LED driver in a 16-lead TSSOP thermally enhanced package. The demonstration circuit is designed to drive two 1.5A 4-LED strings (one on each channel) from an input voltage between 13V and 36V, but the start-up voltage is limited to 30V. The LT3475-1 operates from 4V to 36V so a lower input voltage can be applied with fewer LEDs.
Tools & Simulations
LTspice® is a powerful, fast and free simulation software, schematic capture and waveform viewer with enhancements and models for improving the simulation of analog circuits.
To launch ready-to-run LTspice demonstration circuits for this part:
Step 1: Download and install LTspice on your computer.
Step 2: Click on the link in the section below to download a demonstration circuit.
Step 3: If LTspice does not automatically open after clicking the link below, you can instead run the simulation by right clicking on the link and selecting “Save Target As.” After saving the file to your computer, start LTspice and open the demonstration circuit by selecting ‘Open’ from the ‘File’ menu.
Models for the following parts are available in LTspice:
ADI has always placed the highest emphasis on delivering products that meet the maximum levels of quality and reliability. We achieve this by incorporating quality and reliability checks in every scope of product and process design, and in the manufacturing process as well. "Zero defects" for shipped products is always our goal.
Sample & Buy
The USA list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Analog Devices, Inc. sales office or authorized distributor. Pricing displayed for Evaluation Boards and Kits is based on 1-piece pricing.