Input rail flexibility and the 42V ceiling
The LM25085SDE/NOPB accepts a supply voltage from 4.5V to 42V, which means it runs from a 12V or 24V industrial bus, a 48V telecom rail, or a multi-cell battery string without an external pre-regulator. The 42V absolute maximum (implied by the operating range) covers 36V nominal systems with margin for transients.
Switching frequency and external component sizing
Switching frequency is programmable up to 1 MHz. The trade-off is higher gate-drive loss in the external MOSFET, so the controller's own dissipation stays low, but the FET's switching loss sets the practical ceiling. Because the controller lacks synchronous rectification, the low-side freewheeling diode conducts during the off-time. At high step-down ratios (e.g., 24V to 3.3V), the diode's forward voltage dominates the efficiency loss. A Schottky diode with low Vf is recommended; the controller's 100% duty cycle capability helps at low dropout, where the diode is off for most of the cycle.
Thermal and package integration
The 8-WSON package with exposed pad measures 3 mm × 3 mm.