Dual-phase buck controller for high-current POL rails
The LTC3774IUHE#PBF is a dual-output, dual-phase step-down PWM controller from the PolyPhase series, designed for non-isolated point-of-load regulators that need to share current across two interleaved phases. It drives external N-channel MOSFETs and generates a PWM signal for each phase, reducing input ripple and allowing smaller input capacitors compared to a single-phase design. The input supply range of 4.5 V to 38 V covers common intermediate bus voltages in telecom, industrial, and automotive systems. The switching frequency is programmable from 150 kHz to 1.2 MHz, letting the designer trade efficiency against inductor size. Control features include current limit, enable, frequency control, power good, soft start, and output tracking — enough to sequence multiple rails without an external supervisor.
What the ratings mean for the power stage
The 98% maximum duty cycle keeps the high-side FET on nearly the whole cycle, useful when the input voltage is only slightly above the output target. The -40°C to 125°C junction temperature rating covers both industrial enclosures and under-hood automotive environments. No synchronous rectifier is built in; the external MOSFETs handle the low-side switching, so the designer chooses the FETs for the target efficiency and thermal budget. The 36-QFN (5x6) package with exposed pad requires a thermal via pattern under the part to pull heat into the PCB copper plane. The pad is the main thermal path — a layout review is worth the time.
Lifecycle and compliance
The LTC3774IUHE#PBF is listed as Active with ROHS3 compliance.