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LED controller includes internal PWM generator

Linear Technology Corp. introduces the LT3761, a dc/dc controller designed to operate as a constant-current source and constant-voltage regulator. It also features a programmable internal PWM dimming signal. The LT3761 is well suited for driving high current LEDs, but also has features that make it suitable for charging batteries and supercapacitors.

The fixed frequency, current mode architecture results in stable operation over a wide range of supply and output voltages. A voltage feedback 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 100 kHz to 1 MHz to optimize efficiency, performance, or external component size.

The LT3761 senses output current at the high side or at the low side of the load. The PWM input can be configured to self-oscillate at fixed frequency with duty ratio programmable from 4% to 96%. When driven by an external signal, the PWM input provides LED dimming ratios of up to 3,000:1. The CTRL input provides additional analog dimming capability.

Applications include:

  • High-voltage LED strings >100 V with ground referred current sense
  • Grounded anode LEDs
  • Battery and SuperCap chargers
  • Accurate current limited voltage regulators

Features:
  • 3,000:1 True Color PWM Dimming for LEDs
  • Wide VIN Range: 4.5 to 60 V
  • Rail-to-Rail Current Sense Range: 0 to 80 V
  • Programmable PWM Dimming Signal Generator
  • Constant Current (±3%) and Constant-Voltage (±2%) Regulation
  • Analog Dimming
  • Drives LEDs in Boost, SEPIC, Inverting, Buck Mode, Buck-Boost Mode, or Flyback Configuration
  • Output Short-Circuit Protected Boost
  • Open LED Protection and Reporting
  • Adjustable Switching Frequency: 100 kHz to 1 MHz
  • Programmable VIN UVLO with Hysteresis
  • C/10 Indication for Battery Chargers
  • Low Shutdown Current: <1 μA
  • Thermally Enhanced 16-Lead MSOP Package

For more information, contact Linear Technology Corp., 1630 McCarthy Blvd., Milpitas, CA 95035. Phone: (408) 432-1900.

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