What it is and where it fits
The MAX16821CATI+ is a DC DC controller from Analog Devices, purpose-built for driving LED strings in backlight applications. It is a controller, not a converter with integrated switches — the external MOSFETs handle the power stage, which gives you flexibility to scale the output current and voltage for different LED array sizes. The part supports SEPIC, step-down (buck), and step-up (boost) topologies, so it can regulate a LED string above or below the input rail depending on the layout. PWM dimming is built in, which means you can vary LED brightness by modulating the on-time of the external switch at a frequency independent of the switching regulator loop. That keeps colour temperature stable across the dimming range — important for display backlights and architectural lighting where consistent CCT matters. The switching frequency can be set between 125 kHz and 1.5 MHz. Lower frequencies reduce switching losses and help with thermal management on a tight board; higher frequencies shrink the inductor and capacitor values, saving board area. Pick the sweet spot for your efficiency versus size trade-off.
Supply and temperature — what the ratings mean for the BOM
Input voltage range is 4.75 V to 28 V. Operating temperature spans -40°C to 125°C, which qualifies it for under-hood automotive, outdoor LED signage, and industrial enclosures where ambient can climb. The exposed pad on the 28-TQFN (5x5 mm) package helps pull heat into the PCB ground plane — make sure your layout includes a thermal via array under the pad to keep the junction temperature within limits at full load.
Lifecycle and sourcing
The MAX16821CATI+ is listed as Active with ROHS3 compliance.