The TPS40057 is safe for prebiased outputs, not turning on the synchronous rectifier until the high-side FET has already started switching. The TPS40054 operates in one quadrant and sources output current only, allowing for paralleling of converters and ensures that one converter does not sink current from another converter. This controller also emulates a non-synchronous buck converter at light loads where the inductor current goes discontinuous. At continuous output inductor currents, the controller operates as a synchronous buck converter to optimize efficiency. The TPS40055 operates in two quadrants, sourcing and sinking output current.