The LTC3727/LTC3727-1 are high performance dual step-down switching regulator controllers that drive all N-channel synchronous power MOSFET stages. A constant frequency current mode architecture allows phaselockable frequency of up to 550kHz. Power loss and noise due to the ESR of the input capacitors are minimized by operating the two controller output stages out of phase. OPTI-LOOP compensation allows the transient response to be optimized over a wide range of output capacitance and ESR values. There is a precision 0.8V reference and a power good output indicator. A wide 4V to 30V (36V maximum) input supply range encompasses all battery chemistries. A RUN/SS pin for each controller provides soft-start, and on the LTC3727GN, optional timed, short-circuit shutdown. Current foldback limits MOSFET heat dissipation during short-circuit conditions when overcurrent latchoff is disabled. Output overvoltage protection circuitry latches on the bottom MOSFET until VOUT returns to normal. The FCB mode pin can select among Burst Mode, constant frequency mode and continuous inductor current mode or regulate a secondary winding. The LTC3727/LTC3727-1 include a power good output pin that indicates when both outputs are within 7.5% of their designed set point.