The high-efficiency, pulse-width modulated (PWM), DCto-DC buck converter is optimized to provide a guaranteed output current of 800mA. The output voltage is dynamically controlled to produce any fixed-output voltage in the range of 0.75V to 3.4V (MAX1958) or 1V to 3.6V (MAX1959), with settling time less than 30s for a full-scale change in voltage and current. The 1MHz PWM switching frequency allows the use of small external components while pulse-skip mode reduces quiescent current to 190A with light loads. The converter utilizes a low on-resistance internal MOSFET switch and synchronous rectifier to maximize efficiency and minimize external component count. The 100% duty-cycle operation allows for an IC dropout voltage of only 130mV (typ) at 600mA load.