Demonstration Circuit DC436A is a 1.25MHz 3A monolithic step-down DC/DC switching converter using the LT1765. With its fast switching speed, 3A internal power switch, and wide input voltage range, the LT1765 is a very versatile and powerful IC for dc/dc converters that require compact space and a wide variety of input voltage ranges. The constant 1.25MHz switching frequency allows all of the components to be very small, surface mount devices. The current-mode control topology creates fast transient response and good loop stability with a minimum number of external compensation components and ceramic input and output capacitors. The low Rds(on) internal power switch (0.09?) maintains high efficiencies >80% and up to 90%. The /Shdn pin and 15uA shutdown current extends battery life. The wide Vin range of the LT1765 allows step-down configurations from 3Vin up to 25Vin. Synchronization of switching frequencies up to 2MHz is possible. Demonstration Circuit DC436A is a step-down converter using the LT1765. The circuit is designed for 6.5V to 25V input to 5.0V output at up to 2.5A1 for cable modem, handheld, automotive, and desktop computer applications. This board was designed for wide input voltage range applications where simplicity, small circuit size, and low component count are important as well as up to 2.5A of load current. The use of ceramic capacitors not only demonstrates small size and low cost, but the advantage of current-mode control in step-down applications with a simple compensation network and a feedforward capacitor for more rugged stability and excellent transient response. The components built on the board are optimized a wide input voltage range, but can be reduced in size for input voltages such as 12V if desired. The adjustable feedback resistors also allows for customizable output voltage.