LM3445 Datasheet | National Semiconductor

Description The LM3445 is an adaptive constant off-time AC/DC buck (step-down) constant current controller designed to be 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 dimming using standard triac dimmers. The high frequency capable architecture allows the use of small external passive ponents. 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 directly 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 under-voltage lockout. Features - - - - - - - - - - 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 Applications - - - - Retro Fit Triac Dimming Solid State Lighting Industrial and mercial Lighting Residential Lighting Typical LM3445 LED Driver Application Circuit © 2009 National Semiconductor Corporation .national. Connection Diagram .. Top View 10-Pin MSOP NS Package Number MUB10A Ordering Information Order Number LM3445MM LM3445MMX Spec. NOPB NOPB Package Type MSOP-10 MSOP-10 NSC Package Drawing MUB10A MUB10A Top Mark SULB SULB Supplied As 1000 Units, Tape and Reel 3500 Units, Tape and Reel Pin Descriptions Pin # 1 2 Name ASNS FLTR1 Description PWM output of the triac dim decoder circuit. Outputs a 0 to 4V PWM signal with a duty cycle proportional to the triac dimmer on-time. First filter...