Data Sheet
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Overview

Features and Benefits

  • 3000:1 True Color PWM™ Dimming
  • Wide Input Voltage Range: 4.5V to 80V
  • Output Voltage Up to 80V
  • Internal 3.3A/84V Switch
  • Constant-Current and Constant-Voltage Regulation
  • 250mV High Side Current Sense
  • Drives LEDs in Boost, Buck Mode, Buck-Boost Mode, SEPIC or Flyback Topology
  • Adjustable Frequency: 100kHz to 1MHz
  • Open LED Protection
  • Programmable Undervoltage Lockout with Hysteresis
  • Constant-Voltage Loop Status Pin
  • PWM Disconnect Switch Driver
  • CTRL Pin Adjusts High Side Current Sense Threshold
  • Low Shutdown Current: <1μA
  • Programmable Soft-Start
  • Available in the 36-Lead (5mm × 6mm) QFN Package

Product Details

The LT3956 is a DC/DC converter designed to operate as a constant-current source and constant-voltage regulator. It is ideally suited for driving high current LEDs. It features an internal low side N-channel power MOSFET rated for 84V at 3.3A and driven from an internal regulated 7.15V supply. The fixed frequency, current-mode architecture results in stable operation over a wide range of supply and output voltages. A ground referenced voltage FB pin serves as the input for several LED protection features, and also makes it possible for the converter to operate as a constant-voltage source. A frequency adjust pin allows the user to program the frequency from 100kHz to 1MHz to optimize efficiency, performance or external component size.

The LT3956 senses output current at the high side of the LED string. High side current sensing is the most flexible scheme for driving LEDs, allowing boost, buck mode or buck-boost mode configuration. The PWM input provides LED dimming ratios of up to 3000:1, and the CTRL input provides additional analog dimming capability.

Applications

  • High Power LED
  • Battery Charger
  • Accurate Current Limited Voltage Regulator

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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.

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Documentation & Resources

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    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

    LTspice Simulations

    LT3956 Demo Circuit - 94% Efficient 25W White LED Automotive Headlamp Driver (6-60V to 18x 3.6V LEDs @ 380mA)

    Models for the following parts are available in LTspice:

    LT3956

    Product Recommendations

    LT3956 Companion Parts

    Recommended Related Parts

    Recommended Suggested Oscillator

    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.

    LT3956 Material Declaration
    Quality And Reliability
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    Support & Discussions

    LT3956 Discussions

    RE: LCD Backlight Driver 14,3V @ 600mA with IC LT3956
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