Overview

Features and Benefits

  • Up to 36V of LEDs, 2-String × 60mA LED Driver
  • Wide Input Range: 2.9V to 40V
  • Up to 40,000:1 PWM Dimming (250ns LED On-Time) (Independent of Leakage at VOUT)
  • ±2% LED Current Matching (Typ ±0.3%)
  • Integrated Schottky Diode
  • Internal 400mΩ, 40V, 1A Switch
  • Single Resistor Sets LED Current (10mA to 60mA) for Both High-Side Current Sources
  • Output Adapts to LED VF for Optimum Efficiency
  • LED Current Regulated Even for VIN > VOUT
  • Fault Flag + Protection for Open-LED and LED-Short-to- GND (Other String Remains in Regulation)
  • Programmable Maximum VOUT (Regulated)
  • Internal Compensation, Soft-Start and Thermal Regulation
  • Accurate EN/UVLO Threshold
  • Fixed 2MHz Switching Frequency

Product Details

The LT3909 is a 2-string × 60mA LED driver with a fixed 2MHz step-up DC/DC converter capable of driving up to 36V of LEDs. Each LED string contains an accurate high-side current source with ±2% current matching. Output voltage adapts to variations in LED VF for optimum efficiency.

Maximum LED current can be programmed from 10mA to 60mA per string using a single resistor. LED brightness can be reduced with analog dimming (up to 10:1) or with PWM dimming (up to 40,000:1 at 100Hz, up to 160:1 at 25kHz) (independent of leakage at VOUT). The LED pins can be paralleled for higher LED current.

Additional features include: programmable maximum VOUT for open LED protection, a fault flag to indicate open-LED or LED-short-to-GND and an internal regulation loop to safely limit junction temperature. The LT3909 also includes internal compensation, internal soft-start and micropower shutdown. The LT3909 is available in the 12-pin (3mm × 3mm) DFN and 12-pin MSOP packages.

Applications

  • PDAs, Handheld Computers
  • GPS Receivers
  • Automotive Displays
  • High Contrast Instrument Clusters

Product Lifecycle icon-recommended 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 (1)

Tools & Simulations

LTspice

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.

LTspice

Models for the following parts are available in LTspice:

LT3909

Product Recommendations

LT3909 Companion Parts

Recommended Related Parts

Design Resources

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.

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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.


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Evaluation Boards Pricing displayed is based on 1-piece.
Pricing displayed is based on 1-piece. The USA list pricing shown is for budgetary use only, shown in United States dollars (FOB USA per unit), and is subject to change. International prices may vary due to local duties, taxes, fees and exchange rates.