Two-phase synchronous buck controller for high-current rails
The LTC1709EG-85#PBF is a high-power polyphase DC-DC controller from Analog Devices, designed as a step-down (buck) regulator with two output phases. It drives external N-channel MOSFETs in a synchronous rectifier configuration, which means it can deliver high current with lower ripple and better thermal distribution than a single-phase design. The input supply range spans 4 V to 36 V, covering common industrial rails like 5 V, 12 V, and 24 V, and the switching frequency is programmable from 140 kHz to 310 kHz — lower frequencies favor efficiency, higher frequencies shrink the inductor footprint. Control features include an enable pin, power-good output, and soft-start, making it straightforward to sequence rails in a multi-voltage system.
Package and mounting — SSOP-36 on the board
Housed in a 36-SSOP package with a 0.209-inch (5.30 mm) body width, this is a surface-mount part that sits in a standard SSOP-36 footprint. No exposed thermal pad here — heat dissipation relies on the copper pour and via stitching under the package, so pay attention to the PCB layout guidelines for the power stage.
It fits outdoor telecom cabinets, factory-floor motor drives, and power supplies that see seasonal temperature swings. The 99.5% maximum duty cycle means it can run near dropout — useful when the input rail sags close to the output voltage, as in battery-backed systems.
For a new design, this means you can commit the BOM line without worrying about a sudden EOL.