LED driver controller with buck-boost flexibility
The LT8391AIUFD#PBF is a DC DC controller from Analog Devices designed for LED driving in automotive and lighting applications. It supports both step-down (buck) and step-up (boost) topologies, making it suitable for strings where the LED forward voltage may sit above or below the supply rail. Switching frequency is programmable from 600 kHz to 2 MHz, allowing the designer to trade off inductor size against switching losses. The controller operates from a 4V to 60V supply and can deliver up to 60V output — the same 60V rating on both the input and output sides means the same FET voltage stress applies regardless of direction.
Dimming and thermal grade for automotive LED strings
Dimming is supported via both analog and PWM methods — the PWM input allows high-frequency dimming without color shift, while analog dimming suits applications needing a continuous current adjustment. The single output channel drives an external FET pair (no internal switches), so the current rating is set by the external components, not the controller itself. Rated for -40°C to 125°C junction temperature, this part meets the automotive temperature grade required for under-hood or exterior lighting modules. The 28-QFN package (4x5mm) with exposed pad helps conduct heat to the PCB ground plane — the thermal pad must be soldered to a copper pour for the full current capability.
Active lifecycle and compliance documentation
It is ROHS3 compliant, which covers the full ten restricted substances including the four phthalates added under EU 2015/863. No official second-source or pin-compatible drop-in from another manufacturer is listed — the closest functional peer within the same family is the LT8391EUFD#PBF, which shares the same topology, dimming methods, and package footprint.