What this controller does on the board
The LM3409MYX/NOPB is a constant-current buck controller from Texas Instruments, designed to drive a single string of high-power LEDs. It's a controller, not a regulator — there's no internal switch, so you pair it with an external MOSFET and inductor to handle the load current. The part supports both analog and PWM dimming, which gives you flexibility: analog for continuous current adjustment, PWM for maintaining color temperature at reduced brightness. Input supply range runs from 6V up to 42V, making it a natural fit for automotive lighting where the battery rail can swing from cold-crank to load-dump transients. The operating temperature range of -40°C to 125°C covers under-hood and exterior lighting environments without derating.
Automotive-grade fit — what the ratings mean
The 42V maximum supply voltage is the headline number for automotive work. A nominal 12V or 24V battery system can see transients well above 40V during load dump, and this controller's 42V rating gives you headroom without needing a separate clamping stage. The -40°C to 125°C junction temperature range covers both cold-start at -40°C and the heat soak under the hood in summer. If you're designing for exterior lighting — headlamps, DRLs, taillamps — the wide temperature range and high input voltage are the specs that keep the design from coming back as a field failure.
Package and footprint notes for the layout
The LM3409MYX/NOPB comes in a 10-lead HVSSOP package (3.00 mm width), which is a PowerPAD package. The exposed pad on the bottom is the main thermal path — it needs to be soldered to a copper plane on the PCB, with thermal vias stitching to an inner ground layer. Without that, the junction temperature climbs fast at higher output currents. The NOPB suffix confirms ROHS3 compliance, so no lead in the finish.
Sourcing and lifecycle — still in production
For a BOM line that needs a qualified automotive LED driver controller, this part is a safe choice for both new designs and production replenishment.