1.6MHz, 1A Constant Current Buck LED Driver with Internal Compensation in Tiny SOT-23 Package Evalu


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The LM3405A demo board is configured to drive a series string of high power, high brightness LEDs at a forward current of 1A using the LM3405A constant current buck regulator. The board can accept a full input operating range of 3V to 22V. The converter output voltage adjusts as needed to maintain a constant current through the LED array. The LM3405A is a step-down regulator with an output voltage range extending from a VO(MIN) of 205mV (the reference voltage) to a VO(MAX) determined by the maximum duty cycle (typically 94%). It can drive up to 5 LEDs in series at 1A forward current, with the single LED forward voltage of approximately 3.7V (Typical of white, blue, and green LEDs using InGaN technology).

  • VIN operating range of 3V to 22V
  • Drives up to 5 High-Brightness LEDs in series at 1A
  • Thin SOT23-6 package
  • 1.6MHz switching frequency
  • EN/DIM input for enabling and PWM dimming of LEDs
  • 300mΩ NMOS switch
  • 40nA shutdown current at VIN = 5V
  • Internally compensated current-mode control
  • Cycle-by-cycle current limit
  • Input voltage UVLO
  • Over-current protection
  • Thermal shutdown


  • LED Driver
  • Constant Current Source
  • Industrial Lighting
  • LED Flashlights
  • LED Lightbulbs


Illumination LED drivers
LM3405A 1.6-MHz, 1-A constant current buck LED driver with internal compensation
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Evaluation board

LM3405AEVAL/NOPB — 1.6MHz, 1A Constant Current Buck LED Driver with Internal Compensation in Tiny SOT-23 Package Evalu

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Technical documentation

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Type Title Date
* User guide AN-1685 LM3405A Demo Board (Rev. B) 01 May 2013
Certificate LM3405AEVAL/NOPB EU Declaration of Conformity (DoC) 02 Jan 2019
Application note Powering & Dimming High-Brightness LEDs w/ LM3405 Constant-Current Buck Reg (Rev. A) 01 May 2013
User guide LM3405A Reference Design for MR16 LED Bulb, 600mA User Guide 27 Jan 2012

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