The Industry's First TRIAC Dimmable LED Driver
with Both Full-range and Flicker-free Dimming

  • Overview
  • Features
  • Specifications
  • Eval Board
  • Part Numbers


TRIAC Dimmable LED DriverBest-in-Class Dimming Performance.

National Semiconductor introduces a new constant-current controller that enables off-line, uniform, flicker-free dimming of high-brightness light-emitting diodes (LEDs) with a conventional TRIode for Alternating Current (TRIAC) forward or reverse phase-control wall dimmer. The LM3445 TRIAC dimmable LED driver enables a full 100:1 range of dimming capability and can maintain greater than 1A of constant current to large strings of LEDs in a variety of residential, architectural, commercial and industrial applications.

The LM3445 TRIAC dimmable LED driver maximizes the light output for systems while maintaining ENERGY STAR® power factor requirements in a typical application, which positions it among National's PowerWise® family of energy-efficient products. The new driver will be demonstrated in National's booth #426 at the Applied Power Electronics Conference (APEC) 2009 conference in Washington, D.C., from Feb. 15 to 18.

Today's TRIAC wall dimmers are designed to interface with a resistive load such as incandescent or halogen light bulbs. Since an LED bulb does not appear as a resistive load to the TRIAC wall dimmer, dimming an LED bulb using a conventional TRIAC wall dimmer does not yield optimal dimming performance. LED drivers available today cause either a 120 Hz flicker of the LEDs or do not enable the full 100:1 dimming range. National's LM3445 overcomes this challenge by translating the TRIAC-chopped waveform to a DIM signal and decoding it for a full-range of uniform, flicker-free dimming. The driver's patent-pending control architecture maintains constant ripple through the LEDs, which extends the life of the LEDs.   Datasheet    Product Brief


  • Triac dim decoder circuit for LED dimming
  • Application voltage range 80VAC–270VAC
  • Capable of controlling LED currents greater than 1A
  • Adjustable switching frequency
  • Low quiescent current
  • Adaptive programmable off-time allows for constant ripple current
  • Thermal shutdown
  • No 120Hz flicker
  • Low profile 10 pin MSOP Package
  • Patent pending drive architecture
  • Retro fit triac dimming
  • Solid state lighting
  • Industrial and commercial lighting
  • Residential lighting


RoHS Compliant


Absolute Maximum Ratings (Notes 1, 2)
BLDR to GND –0.3V to +17V
VCC, GATE, FLTR1 to GND –0.3V to +14V
ISNS to GND –0.3V to +2.5V
ASNS, DIM, FLTR2, COFF to GND –0.3V to +7.0V
COFF Input Current 100mA
Continuous Power Dissipation Internally Limited (Note 3)
HBM (Note 4) 2kV
Junction Temperature (TJ-MAX) 150°C
Storage Temperature Range -65°C to +150°C
Maximum Lead Temp. Range (Soldering) 300°C
Operating Conditions
VCC 8.0V to 12V
Junction Temperature –40°C to +125°C

  Connection Diagram
  Simplified Internal Block Diagram

Note 1:  Absolute maximum ratings are limits beyond which damage to the device may occur. Operating ratings are conditions for which the device is intended to be functional, but device parameter specifications may not be guaranteed. For guaranteed specifications and test conditions, see the Electrical Characteristics in the Datasheet
Note 2:  All voltages are with respect to the potential at the GND pin, unless otherwise specified.
Note 3:  Internal thermal shutdown circuitry protects the device from permanent damage. thermal shutdown engages at TJ=165°C (typ.) and disengages at TJ=145°C (typ.).
Note 4:  Human Body Model, applicable std. JESD22-A114-C.

Eval Board

LM3445 Evaluation BoardEvaluation Board LM3445TRIACEVAL
The LM3445 Off-Line TRIAC Dimmer LED board converts 90VAC to 135VAC input, and drives seven or eight series connected LEDs at 350mA average current. The LM3445 switching frequency is set at a nominal 225 kHz. This is a four-layer board using the bottom and top layer for component placement. The demonstration board can be modified to adjust the LED forward current, the number of series connected LEDs and switching frequency.   Buy Now!

– LM3445TRIAC Assembled Evaluation Board
Application Note 1935 for the LM3445TRIAC Evaluation Board

Part Numbers

National Semiconductor
Part Number
Part Number
Tape & Reel
  IC - TRIAC Dimmable LED Driver, MSOP-10
Cut Tape
  Eval Board - Off-Line TRIAC Dimmer LED Driver