LT3478

PRODUCTION

4.5A Monolithic LED Drivers with True Color PWM Dimming

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Overview

  • True Color PWM™ Dimming Delivers Constant LED Color with Up to 3000:1 Range
  • Wide Input Voltage Range: 2.8V to 36V
  • 4.5A, 60mΩ, 42V Internal Switch
  • Drives LEDs in Boost, Buck-Boost or Buck Modes
  • Integrated Resistors for Inductor and LED Current Sensing
  • Program LED Current:
    • 100mA to 1050mA (LT3478-1)
    • (10mV to 105mV)/RSENSE (LT3478)
  • Program LED Current De-Rating vs Temperature
  • Separate Inductor Supply Input
  • Inrush Current Protection
  • Programmable Soft-Start
  • Fixed Frequency Operation from 200kHz to 2.25MHz
  • Open LED Protection (Programmable OVP)
  • Accurate Shutdown/UVLO Threshold with Programmable Hysteresis
  • 16-Pin Thermally Enhanced TSSOP Package

The LT3478/LT3478-1 are 4.5A step-up DC/DC converters designed to drive LEDs with a constant current over a wide programmable range. Series connection of the LEDs provides identical LED currents for uniform brightness without the need for ballast resistors and expensive factory calibration.

The LT3478-1 reduces external component count and cost by integrating the LED current sense resistor. The LT3478 uses an external sense resistor to extend the maximum programmable LED current beyond 1A and also to achieve greater accuracy when programming low LED currents. Operating frequency can be set with an external resistor from 200kHz up to 2.25MHz. Unique circuitry allows a PWM dimming range up to 3000:1 while maintaining constant LED color. The LT3478/LT3478-1 are ideal for high power LED driver applications such as automotive TFT LCD backlights, courtesy lighting and heads-up displays. One of two CTRL pins can be used to program maximum LED current. The other CTRL pin can be used to program a reduction in maximum LED current vs temperature to maximize LED usage and improve reliability.

Additional features include inrush current protection, programmable open LED protection and programmable soft-start. Each part is available in a 16-pin thermally enhanced TSSOP Package.

Applications

  • High Power LED Driver
  • Automotive Lighting
LT3478
4.5A Monolithic LED Drivers with True Color PWM Dimming
Automotive TFT LCD Backlight Efficiency vs VIN Product Package 1
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Documentation

Data Sheet 1

Reliability Data 1

User Guide 1

Technical Articles 1

Data Sheet

This is the most up-to-date revision of the Data Sheet.

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Software Resources

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Hardware Ecosystem

Parts Product Life Cycle Description
Analog to Digital Converters (ADCs) 1
LTC2991
RECOMMENDED FOR NEW DESIGNS Octal I2C Voltage, Current, and Temperature Monitor
Digital to Analog Converters (DACs) 1
LTC2657
PRODUCTION Octal I2C 16-/12-Bit Rail-to-Rail DACs with 10ppm/°C Max Reference
Protection Switches & Controllers 1
LT4363
RECOMMENDED FOR NEW DESIGNS High Voltage Surge Stopper with Current Limit
Pulse-Width Modulation (PWM) & Pulse Generators 1
LTC6992
TimerBlox: Voltage-Controlled Pulse Width Modulator (PWM)
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Tools & Simulations

LTspice 1

Models for the following parts are available in LTspice:

  • LT3478
  • LT3478-1
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.

Evaluation Kits

eval board
schematic 1
DC949A-A

LT3478EFE-1 Demo Board | Boost LED Driver, Internal RSENSE, 2.8V ≤ VIN ≤ 25V, VLED up to 36V @ 350mA

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Product Details

Demonstration circuit 949A is a 4.5A peak switch current boost LED driver with PWM dimming featuring the LT3478/LT3478-1. The LT3478 can be used for boost, buck mode, and buck-boost mode LED drivers. DC949A-A includes the LT3478-1, a fixed 1A boost LED driver with the LED current sense resistor inside the IC. DC949A-B features the LT3478 adjustable current boost LED driver; it requires an external sense resistor (R11). Both circuits are optimized to drive a 350mA LED string with a total LED voltage above the input voltage and below 40V (overvoltage protection is set between 36V and 40V).


The IC's input voltage range is 2.8V to 16V and the LED power input voltage range is 2.8V to 25V (for VLED >25V). With an internal 4.5A NPN power switch, floating current sense amplifier, LED current PWM dimming control, inrush current protection, programmable switching frequency, soft-start, and overvoltage protection, the LT3478-1/LT3478 are extremely powerful and versatile LED driving

eval board
schematic 2
DC949A-B

LT3478EFE Demo Board | Boost LED Driver, Adjustable LED Current, 2.8V ≤ VIN ≤ 25V, VLED up to 36V @ 350mA

Buy Now View Details

Product Details

Demonstration circuit 949A is a 4.5A peak switch current boost LED driver with PWM dimming featuring the LT3478/LT3478-1. The LT3478 can be used for boost, buck mode, and buck-boost mode LED drivers. DC949A-A includes the LT3478-1, a fixed 1A boost LED driver with the LED current sense resistor inside the IC. DC949A-B features the LT3478 adjustable current boost LED driver; it requires an external sense resistor (R11). Both circuits are optimized to drive a 350mA LED string with a total LED voltage above the input voltage and below 40V (overvoltage protection is set between 36V and 40V).


The IC's input voltage range is 2.8V to 16V and the LED power input voltage range is 2.8V to 25V (for VLED > 25V). With an internal 4.5A NPN power switch, floating current sense amplifier, LED current PWM dimming control, inrush current protection, programmable switching frequency, soft-start, and overvoltage protection, the LT3478-1/LT3478 are extremely powerful and versatile LED driving ICs.
DC949A-A
LT3478EFE-1 Demo Board | Boost LED Driver, Internal RSENSE, 2.8V ≤ VIN ≤ 25V, VLED up to 36V @ 350mA
DC949A-A - Schematic
DC949A-B
LT3478EFE Demo Board | Boost LED Driver, Adjustable LED Current, 2.8V ≤ VIN ≤ 25V, VLED up to 36V @ 350mA
DC949A-A - Schematic

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