Buck regulator, 3.5 A continuous, 40 V input ceiling
The LMR14030SSQDDAQ1: The output is adjustable from 0.8 V up to 28 V, set by a resistor divider on the FB pin.
Switching frequency and external diode — no synchronous rectifier
Switching frequency is programmable via the RT pin from 200 kHz to 2.5 MHz. A lower frequency reduces switching losses but requires a larger inductor; 2.5 MHz keeps the magnetics small for space-constrained automotive PCBs. The part uses an external Schottky catch diode — it does not integrate a synchronous rectifier. This means the BOM adds a diode, but the trade-off is lower cost and no shoot-through risk at high input voltage. The diode's forward voltage and thermal rating must be sized for the 3.5 A peak inductor current.
8-PowerSOIC with exposed pad — thermal and layout notes
The input capacitor should be placed within 5 mm of the VIN pin to keep the high-frequency loop small. The SW pin node sees fast voltage transitions; keep the catch diode and inductor connection short to reduce radiated emissions.