8-channel LED driver offers efficient TFT-LCD backlighting solutions

Linear Technology has unveiled an 8-channel LED driver, utilizing a step-up DC/DC controller capable of driving up to a 45 V string of 100 mA LEDs per channel.

The LT3760's internal 60 V, 1 MHz DC/DC boost mode controller is designed to operate as a constant current LED driver for up to 80 white LEDs. From a 12 V input, the LT3760 can drive 8 channels, each with up to ten 100 mA white LEDs in series while delivering efficiencies exceeding 92 percent. The device's multichannel capability makes it ideal for medium and large-sized TFT-LCD backlighting applications. Its input voltage range of 6 V to 40 V makes it ideal for automotive, avionic, HDTV and industrial display applications.

The LT3760 offers ±2.0 percent (±0.7 percent typical) LED current matching to ensure uniform brightness of the display. Dimming ratios as high as 3,000:1 can be attained by using True Color PWM dimming. A programmable 100 kHz to 1 MHz fixed frequency operation and current mode architecture offers stable operation over a wide range of supply and output voltages while minimizing the size of the external components. Additionally, the switching frequency is synchronizable to an external clock. Its thermally enhanced TSSOP-28 package offers a highly compact solution footprint for most LED backlighting applications.

The LT3760 uses an external N-Channel MOSFET switch to provide a boost mode constant current source. However, even when VIN exceeds VOUT, the LT3760 will continue to accurately regulate the LED current. The internal boost controller uses an adaptive feedback loop to drive up to eight channels of ten 100 mA LEDs to regulate the output voltage slightly higher than the required LED voltage to ensure maximum efficiency. If any of the LED strings experience an open circuit, the LT3760 will continue to regulate the existing strings and signal the FAULT alert pin. If higher current LEDs are required, multiple strings can be combined, enabling the LT3760 to drive up to four channels of ten 200 mA LEDs or two channels of ten 400 mA LEDs. Additional features include programmable LED current derating based on junction temperature and LED temperature and programmable output voltage limiting when all LED strings are disconnected.

Summary of Features: LT3760

  • Up to 45 V of LEDs x 100 mA, 8-Channel LED Driver
  • Wide Input Range: 6 V to 40 V
  • ±2.0 percent LED Current Matching at 20 mA (Typ ±0.7 percent)
  • Up to 3000:1 True Color PWM Dimming Range
  • Single Resistor Sets LED Current (20 mA to 100 mA)
  • LED Current Regulated Even for PVIN > VOUT
  • Output Adapts to LED VF for Optimum Efficiency
  • Fault Flag + Protection for Open LED Strings
  • Protection for LED Pin to VOUT Short
  • Parallel Channels for Higher LED Current
  • Programmable LED Current Derating vs. Temperature
  • Accurate Undervoltage Lockout Threshold with Programmable Hysteresis
  • Programmable Frequency (100 kHz to 1 MHz)
  • Synchronizable to an External Clock

  • Thermally Enhanced 28-Pin TSSOP Package

Availability and Pricing

The LT3760EFE is available in a thermally enhanced 28-lead TSSOP package and is priced at $4.25 each in 1,000 piece quantities. An industrial grade version, the LT3760IFE is tested and guaranteed to operate from a -40 to 125 degrees C operating junction temperature and is priced at $5.00 each in 1,000-piece quantities. All versions are available from stock.



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