Using an isolated power supply to power the high-side device has the advantage that it will work regardless of continued power-stage switching or duty cycle. It can also power the high-side device before power-stage switching begins, eliminating the power-loss concern of switching with an unpowered LMG352xR030-Q1 (see Section 10.2.2.1.1 for details). Finally, a properly-selected isolated supply will introduce less parasitics and reduce noise coupling.
The isolated supply can be obtained with a push-pull converter, a flyback converter, a FlyBuck™ converter, or an isolated power module. When using an unregulated supply, the input of LMG352xR030-Q1 should not exceed the maximum supply voltage. A 16-V TVS diode could be used to clamp the VDD voltage of LMG352xR030-Q1. Minimizing the inter-winding capacitance of the isolated power supply or transformer is necessary to reduce switching loss in hard-switched applications.