The NCP1500 is a dual mode converter that operates as either a pulse width modulated (PWM) buck converter or as a linear regulator. The converter automatically transitions between the two modes. The converter operates as a PWM when a synchronization signal is present at the sync input. The converter operates as a linear regulator in the absence of a synchronization signal. The PWM mode offers excellent performance at normal to heavy loads at the sacrifice of output ripple voltage. The linear mode offers excellent noise rejection at the sacrifice of system efficiency. The user is able to select which mode will give the best performance for a given operating condition. Internal protection features include thermal shutdown with hysteresis and cycle-by-cycle current limit in the PWM mode. Additionally, the converter transitions into PFM mode at very light loads if a synchronization signal is present and an output overvoltage condition is detected.