1 A buck LED driver in a TSOT-23-6 footprint
The Texas Instruments LM3405XMKX/NOPB is a current-mode, fixed-frequency buck converter designed to drive a single LED string at up to 1 A from a 3 V to 15 V input rail. The internal switch handles the full 1 A load, so no external FET is needed; the compensation network is integrated, leaving only the inductor, input/output caps, and a sense resistor as the bill-of-materials adders.
PWM dimming and thermal limits
Dimming is done via a PWM signal on the EN pin — the part toggles the full 1 A output at the PWM frequency, giving a linear dimming curve from 0 % to 100 % duty cycle as long as the PWM period stays above the 1.6 MHz switching cycle. The output voltage can be set up to 13.5 V, which accommodates a string of three to four white LEDs in series (each with a ~3 V forward drop) plus the 200 mV sense resistor voltage.
Active production and compliance
RoHS3 compliant with no exemptions; the TSOT-23-6 package is lead-free and compatible with standard reflow profiles (260 °C peak).