The MAX1623 switch-mode buck regulator with synchronous rectification provides local CPU and bus-termination power in notebook and desktop computers. An internal 55m (typ), 3A PMOS power switch and 60m ( typ), 3A NMOS synchronous-rectifier switch deliver continuous load currents up to 3A from a 5V supply with 95% typical efficiency. Output accuracy is 1%, including line and load regulation. The MAX1623 features constant-off-time, current-mode pulse-width-modulation (PWM) control with switching frequencies as high as 350kHz. An external resistor at the TOFF pin sets the off-time, allowing optimum design flexibility in terms of switching frequency, output switching noise, and inductor size. This device is available in a space-saving 20-pin SSOP package.