An internal inverting buck-boost converter generates a regulated negative rail for the turn-off supply of the GaN device. The buck-boost converter is controlled by a peak current mode, hysteretic controller. In normal operation, the converter remains in discontinuous-conduction mode, but may enter continuous-conduction mode during startup and overload conditions. The converter is controlled internally and requires only a single surface-mount inductor and output bypass capacitor. For recommendations on the required passives, see Buck-Boost Converter Design.