7.3.1 High Voltage Start-up Regulator

The LM5141-Q1 contains an internal high voltage VCC bias regulator that provides the bias supply for the PWM controller and the gate drivers for the external MOSFETs. The input pin (VIN) can be connected directly to an input voltage source up to 65 V. The output of the VCC regulator is set to 5 V. When the input voltage is below the VCC set-point level, the VCC output will track VIN with a small voltage drop. In high voltage applications extra care should be taken to ensure the VIN pin does not exceed the absolute maximum voltage rating of 70 V including line or load transients. Voltage ringing on the VIN pin that exceeds the absolute maximum ratings can damage the IC. Use a high quality bypass capacitor between VIN and ground to minimize ringing.