Automotive dual-phase buck controller with 150°C junction rating
The LTC7805RUFDM#PBF is a dual-output synchronous buck controller from Analog Devices, designed for automotive power-train and chassis-domain DC-DC converters. Its AEC-Q100 qualification (Grade 0 implied by the 150°C junction rating) means it passes the full automotive reliability stress suite — temperature cycling, HAST, and ESD — required for under-hood or transmission-mounted ECUs. The 4.5V to 40V input range covers 12V and 24V automotive rails with margin for load-dump transients (up to 40V) and cold-crank dips down to 4.5V. The 100% duty cycle capability lets the top MOSFET stay on when the input voltage falls near the output — critical during engine cranking when the battery voltage sags below 6V. Switching frequency is programmable from 100kHz to 3MHz via a resistor on the RT pin. At 2MHz the inductor footprint shrinks to a 4x4mm shielded type, while the 100kHz end of the range maximizes efficiency at heavy loads. The part does not support clock synchronization — the oscillator runs free at the set frequency.
Package, footprint, and thermal considerations
Housed in a 28-lead WFQFN with exposed pad (4x5mm body, 0.5mm pitch). The wettable-flank option (RUF suffix) creates a visible solder fillet on the package side — this allows automated optical inspection (AOI) of the solder joint, a requirement for automotive PCBA quality gates. The exposed pad must be soldered to a thermal via array on the PCB ground plane to achieve the rated junction-to-ambient thermal resistance. Without the pad connection, the 150°C junction rating is unreachable at full load — the die self-heats above the silicon limit. The part is shipped in tube packaging (50 units per tube). For high-volume reflow, request the tape-and-reel option (LTC7805RUFDM#TRPBF) — the tube variant is intended for prototype builds and low-volume production.
Active lifecycle and sourcing posture
ROHS3 compliant (exemption-free), which satisfies full automotive RoHS conformance requirements. Sourced through authorized distribution channels — quoted to order against the BOM quantity. No stock-holding claim; availability and current pricing confirmed at RFQ. The date-code and lot trace back to the Analog Devices factory; the laser-etched marking on the QFN top matches the manufacturer's plant code for that week — a clean chain for counterfeit screening.