The UC3874 family of synchronous step-down (Buck) regulators provides high efficiency power conversion from an input voltage range of 4.5 to 36 volts. The UC3874 is tailored for battery powered applications such as laptop computers, consumer products, communications systems, and aerospace which demand high performance and long battery life. The synchronous regulator replaces the catch diode in the standard buck regulator with a low Rds(on) N-channel MOSFET switch allowing for significant efficiency improvements. The high side N-channel MOSFET switch is driven out of phase from the low side N-channel MOSFET switch by an on-chip bootstrap circuit which requires only a single external capacitor to develop the regulated gate drive. Fixed frequency, average current mode control provides the regulator with inherent slope compensation, tight regulation of the output voltage, and superior load and line transient response. Switching frequencies up to 300kHz are possible.