A DC/DC controller that doesn't need an internal switch
The LT3755EMSE-2#PBF is a DC/DC controller from Analog Devices built for driving high-brightness LEDs. It's a controller, not a converter — there's no internal switch, so you pick the external MOSFET and inductor to match the load current and topology. That means it handles boost, buck, flyback, and SEPIC configurations, making it a single BOM line for a range of LED strings from a few hundred milliamps to several amps, depending on the external components.
100 kHz to 1 MHz — where the frequency lands matters
The switching frequency is programmable from 100 kHz to 1 MHz. A lower frequency cuts switching losses and lets you use a bigger inductor with lower core loss, which helps in thermally constrained enclosures. Crank it to 1 MHz and you shrink the magnetics and output capacitor, but you'll need to watch gate-drive losses and layout parasitics. The frequency pin accepts a resistor to ground — no external clock needed.
4.5 V to 40 V supply — automotive and industrial rails
The input range runs from 4.5 V up to 40 V. That 4.5 V minimum means it starts from a standard 5 V rail or a single Li-ion cell, and the 40 V ceiling covers 24 V industrial buses and 12 V automotive systems with load-dump transients (as long as you add external clamping).
Analog and PWM dimming — two ways to control brightness
Dimming is supported in both analog and PWM modes. Analog dimming adjusts the LED current linearly via a control voltage, which is simple and noise-free. PWM dimming switches the LED string at a frequency above visible flicker, giving a wider dimming range and better color consistency — useful in architectural or backlighting designs where the LED current must stay constant during the on-time.
Package and thermal — the exposed pad is your friend
It comes in a 16-lead MSOP with an exposed pad. That pad is the main thermal path — without a via stitch to the ground plane under the part, the junction temperature will climb fast above 400 mA continuous output. The pad is also the GND connection, so the PCB layout needs a solid thermal and electrical connection. The mounting is surface-mount, so reflow profiles follow the standard MSOP-EP footprint.