Input range and switching frequency — the two numbers that size the power stage
The TPS40190DRCT accepts a 4.5 V to 15 V supply rail, which covers standard 5 V, 9 V, and 12 V intermediate buses used in industrial and telecom equipment. Switching at 300 kHz, the controller lets you use a smaller inductor than a 100 kHz design, but the 85 % max duty cycle means the output voltage must stay below about 12.75 V from a 15 V input — enough for a 12 V rail but not a 5 V rail from a 5.5 V input.
Synchronous rectifier and temperature grade — efficiency and environment
The built-in synchronous rectifier replaces the external freewheeling diode with a low-side FET driver, boosting efficiency by several points at high current — expect 90 %+ in a well-laid-out 12 V to 3.3 V conversion at a few amps.
ROHS3 compliant, so it passes the EU material restriction for new designs without exemption paperwork.