The LM25116 is a 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 using an emulated current ramp. Current mode control provides inherent line feedforward, 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 operating frequency is programmable from 50 kHz to 1 MHz. The LM25116 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 low quiescent current shutdown disables the controller and consumes less than 10 µA of total input current. Additional features include a high voltage bias regulator, automatic switch-over to external bias for improved efficiency, thermal shutdown, frequency synchronization, cycle-by-cycle current limit and adjustable line undervoltage lockout. The device is available in a power enhanced 20-pin HTSSOP package featuring an exposed die attach pad to aid thermal dissipation. New products (LM25141, LM5141, LM25148, and LM25149) offer reduced BOM cost, higher efficiency, and reduced design size among many other features.