What the 42V input range and 1MHz switching mean for your rail
The LM25085MM/NOPB is a current-mode buck controller from Texas Instruments that steps down a 4.5V to 42V input rail to a regulated output using an external transistor driver. The 42V maximum input covers 24V industrial rails with margin for transients, and the 100% duty cycle capability lets the output ride through brief input dips without dropping regulation. Switching up to 1MHz lets the designer shrink the inductor and output capacitor, trading switching loss for board area — the controller itself does not integrate the FET, so the external MOSFET's gate charge sets the practical frequency ceiling.