LM3445_10 Datasheet, PDF (1/26 Pages) National Semiconductor (TI) – Triac Dimmable Offline LED Driver

LM3445
September 22, 2010
Triac Dimmable Offline LED Driver
General Description
The LM3445 is an adaptive constant off-time AC/DC buck
(step-down) constant current controller designed to be com-
patible with triac dimmers. The LM3445 provides a constant
current for illuminating high power LEDs and includes a triac
dim decoder. The dim decoder allows wide range LED dim-
ming using standard triac dimmers. The high frequency ca-
pable architecture allows the use of small external passive
components. The LM3445 includes a bleeder circuit to ensure
proper triac operation by allowing current flow while the line
voltage is low to enable proper firing of the triac. A passive
PFC circuit ensures good power factor by drawing current di-
rectly from the line for most of the cycle, and provides a
constant positive voltage to the buck regulator. Additional
features include thermal shutdown, current limit and V_CC un-
der-voltage lockout.
Features
■ ^{Triac dim decoder circuit for LED dimming}
■ ^{Application voltage range 80V}_AC ^{– 277V}_AC
■ ^{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 or 14 pin SOIC}
■ ^{Patent pending drive architecture}
Applications
■ ^{Retro Fit Triac Dimming}
■ ^{Solid State Lighting}
■ ^{Industrial and Commercial Lighting}
■ ^{Residential Lighting}
Typical LM3445 LED Driver Application Circuit
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