The LTC®3851 is a high performance synchronous step-down switching regulator controller that drives an all N-channel synchronous power MOSFET stage. A con stant frequency current mode architecture allows a phase-lockable frequency of up to 750kHz. OPTI-LOOP compensation allows the transient response to be optimized over a wide range of output capacitance and ESR values. The LTC3851 features a precision 0.8V reference that is compatible with a wide 4V to 38V input supply range. The TK/SS pin ramps the output voltage during start-up. Current foldback limits MOSFET heat dissipation during short-circuit conditions. The MODE/PLLIN pin selects among Burst Mode operation, pulse skipping mode or continuous inductor current mode at light loads and allows the IC to be synchronized to an external clock.