The LM5119 is a dual synchronous buck controller intended for step-down regulator applications from a high voltage or widely varying input supply. The control method is based upon current mode control utilizing an emulated current ramp. Current mode control provides inherent line feed-forward, cycle-by-cycle current limiting and ease of loop compensation. The use of an emulated control ramp reduces noise sensitivity of the pulse-width modulation circuit, allowing reliable control of very small duty cycles necessary in high input voltage applications. The switching frequency is programmable from 50kHz to 750kHz. The LM5119 drives external high-side and low-side NMOS power switches with adaptive dead-time control. A user-selectable diode emulation mode enables discontinuous mode operation for improved efficiency at light load conditions. A high voltage bias regulator with automatic switch-over to external bias further improves efficiency. Additional features include thermal shutdown, frequency synchronization, cycle-by-cycle and hiccup mode current limit and adjustable line under-voltage lockout. The device is available in a power enhanced leadless LLP-32 package featuring an exposed die attach pad to aid thermal dissipation.