Offline LED driver with Triac dimming — what it does and where it fits
The Texas Instruments LM3445MM/NOPB is an AC DC Offline Switcher controller designed for LED lighting applications that require Triac dimming compatibility. It uses a Step-Down (Buck) topology, operates from an 8V to 12V supply, and switches at a frequency adjustable from 30kHz to 1MHz. The controller has no internal power switch — it drives an external MOSFET — and delivers a single regulated output. The 10-VSSOP package suits compact LED driver boards in retrofit bulbs, downlights, and other mains-powered luminaires where dimmer compatibility is needed.
Temperature range and environment
Rated for -40°C to 125°C junction temperature, this part covers industrial and outdoor lighting enclosures where ambient heat builds up. The wide range also accommodates automotive exterior lighting if the supply rail is derived from the vehicle's 12V bus — though the part itself is not AEC-Q100 listed in the record.
Switching frequency — inductor sizing vs efficiency
The 30kHz to 1MHz range lets you trade inductor size against switching losses.
No internal switch — external MOSFET required
Because the LM3445MM/NOPB has no internal switch, the BOM includes an external MOSFET and its gate-drive components. This adds board area but gives flexibility to choose the FET based on the output current and voltage stress of the specific LED load. For a 1A output at 12V, a small SOT-23 MOSFET suffices; higher currents need a larger DPAK or similar.
Lifecycle and sourcing
The LM3445MM/NOPB is listed as Active with ROHS3 compliance.