The LTC3879 is a synchronous step-down switching regulator controller optimized for high switching frequency and fast transient response. The constant on-time valley current mode architecture allows for a wide input range, including very low duty factor operation. No external sense resistor or slope compensation is required. System flexibility is offered through a user-programmable soft-start pin and independent RUN pin. The voltage ramping soft-start function can be programmed with a capacitor or made to track an external reference source.Operating frequency is set by an external resistor and compensated for variations in VINto offer excellent line stability. Discontinuous mode operation provides high efficiency during light load conditions. A forced continuous control pin allows the user to reduce noise and RF interference. Safety features include output overvoltage protection and programmable current limit with foldback. The current limit is user programmable.The LTC3879 allows operation from 4V to 38V at the input and from 0.6V to 90% VINat the output. The LTC3879 is available in a small 16-pin thermally enhanced MSOP or 3mm × 3mm QFN packages.ApplicationsDistributed Power SystemsEmbedded ComputingCommunications Infrastructure