The LTC3447 is a high efficiency monolithic synchronous current mode buck regulator. Using an I2C interface, the output voltage can be set between 0.69V and 2.05V using an internal 6-bit DAC.The buck regulator has optional external feedback resistors that can be used for setting the initial start up voltage. The feedback voltage reference for this start-up option is 0.6V. Once the voltage DAC is updated via the I2C, the buck regulator switches from external to internal feedback resistors. When there are no external resistors, the default start-up voltage is 1.38V.The switching frequency is internally set at 1MHz, allowing the use of small surface mount inductors and capacitors.In Burst Mode®operation, supply current is only 33µA, dropping to <1µA in shutdown. The 2.5V to 5.5V input voltage range makes the LTC3447 ideally suited for single cell Li-Ion battery-powered applications. 100% duty cycle capability provides low dropout operation, extending battery life in portable systems. Automatic Burst Mode operation increases efficiency at light loads, further extending battery life.The internal synchronous switch increases efficiency and eliminates the need for an external Schottky diode.Protected by U.S. Patents, including 5481178, 6580258, 6304066, 6127815, 6498466, 6611131.ApplicationsDistributed Power SuppliesNotebook ComputersPDAs and Other Handheld Devices