SNVSBZ3 June 2021 LM5168-Q1
The LM516x-Q1 contains an internal linear regulator that is powered from VIN with a nominal output of 5 V, eliminating the need for an external capacitor to stabilize the linear regulator. The internal VCC regulator supplies current to internal circuit blocks, including the synchronous FET driver and logic circuits. The input pin (VIN) can be connected directly to line voltages up to 120 V. Since the power MOSFET has a low total gate charge, use a low bootstrap capacitor value to reduce the stress on the internal regulator. It is required to select a high-quality 2.2-nF 50-V X7R ceramic bootstrap capacitor as specified in the Absolute Maximum Ratings. Selecting a higher value capacitance stresses the internal VCC regulator and damages the device. A lower capacitance than required is not sufficient to drive the internal gate of the power MOSFET. An internal diode connects from the VCC regulator to the BST pin to replenish the charge in the high-side gate drive bootstrap capacitor when the SW voltage is low.