Step-down regulator for wide-VIN industrial rails
The MAX5035AUSA+ is a fixed 3.3 V output, 1 A capable step-down (buck) switching regulator from Analog Devices, designed for applications where the input rail spans 7.5 V to 76 V. The 125 kHz switching frequency keeps external inductor and capacitor values moderate, while the non-synchronous topology (external catch diode required) is a deliberate choice for high input voltage operation where a synchronous FET would add complexity and cost.
Input voltage headroom and output current budget
With a minimum input of 7.5 V and maximum of 76 V, this regulator handles 12 V, 24 V, 48 V, and even 72 V industrial bus voltages without an external pre-regulator. The 1 A continuous output current is specified across the full input range, but the actual power dissipation in the 8-SOIC package limits the achievable output at high VIN — the junction temperature rise from the internal switch's Rds(on) must be checked against the 85°C ambient ceiling. The 3.3 V fixed output eliminates the need for an external feedback divider, saving two resistors and one PCB trace. The 125 kHz switching frequency is low enough to avoid AM radio band interference in sensitive environments, but the inductor ripple current is higher than a 500 kHz design would deliver — select an inductor with a saturation rating above the peak current, not just the DC output.
Package, footprint, and thermal routing
The 8-SOIC (0.154-inch body width, 3.90 mm) package with a standard 1.27 mm pin pitch is a low-cost, widely available footprint. The MAX5035AUSA+ does not expose a thermal pad — all heat is conducted through the leads and the copper on the PCB. A 1 oz copper pour on the top layer under the package, with vias to an internal ground plane, is the recommended thermal management for sustained 1 A operation at high VIN. The tube packaging (50 units per tube typical for 8-SOIC) is suitable for hand-assembly or low-volume production. For automated pick-and-place, a tape-and-reel option may exist under a different order code suffix — verify the packaging code with the BOM quantity before committing.