What the MAX1651ESA+ is and where it fits
The Maxim Integrated MAX1651ESA+ is a step-down (buck) switching regulator controller designed for non-isolated DC-DC conversion. It drives an external transistor switch at frequencies up to 300kHz, making it suitable for medium-power point-of-load regulation in industrial control, telecom, and embedded systems. The 3V to 16V supply range covers common 5V and 12V rails, and the -40°C to 85°C operating temperature grade fits factory-floor and outdoor telecom enclosures without requiring an extended-range part.
Switching frequency and inductor sizing
The MAX1651ESA+ switches at up to 300kHz. The part does not include a clock-sync pin, so it runs free-running.
Supply range and output configuration
With a Vcc range of 3V to 16V, this controller can regulate from a 5V logic rail or a 12V intermediate bus. The output is configured as positive, single-phase, driving an external transistor—no internal FET, so the designer picks the switch based on the load current. The 96.5% maximum duty cycle means it can run near dropout, useful when the input is only a volt or two above the output target.
Package and handling
The MAX1651ESA+ comes in an 8-pin SOIC (0.154" body width, 3.90 mm wide), surface-mount, shipped in tube. The SOIC-8 footprint is standard and easy to hand-solder or reflow. No moisture-sensitive level is stated in the listing, but as a general practice for SOIC packages, store the reels dry if the bake time is unknown—especially if the part has been on the shelf for a while.
Lifecycle and sourcing
The MAX1651ESA+ is listed as Active with ROHS3 compliance. For BOM planning, this means no immediate LTB risk—good for both new designs and sustaining production.