The LM5145 operational input voltage range is from 6 V to 75 V. The device is intended for step-down conversions from 12-V, 24-V, 48-V, 60-V, and 72-V unregulated, semiregulated, and fully-regulated supply rails. The application circuit in Figure 8-1 shows all the necessary components to implement an LM5145-based wide-V_IN step-down regulator using a single supply. The LM5145 uses an internal LDO subregulator to provide a 7.5-V VCC bias rail for the gate drive and control circuits (assuming the input voltage is higher than 7.5 V plus the necessary subregulator dropout specification).

Figure 8-1 Schematic Diagram for VIN Operating Range of 6 V to 75 V

In high voltage applications, take extra care to ensure the VIN pin does not exceed the absolute maximum voltage rating of 105 V during line or load transient events. Voltage ringing on the VIN pin that exceeds the Section 7.1 can damage the IC. Use high-quality ceramic input capacitors to minimize ringing. An RC filter from the input rail to the VIN pin (for example, 4.7 Ω and 0.1 µF) provides supplementary filtering at the VIN pin.