Unlike the Surge Stoppers discussed so far which linearly regulate the output voltage, the LTC7860 employs PWM switching for the output regulation. During normal operation, the LTC7860 turns on an external P-channel MOSFET continuously with 100% duty cycle to pass the input voltage to the output with minimum conduction loss. During an input overvoltage condition, the LTC7860 controls the external MOSFET to operate as a high efficiency switching DC/DC regulator to protect critical downstream components by limiting the output voltage and current. The power handling capability of a Surge Stopper is limited by the power lost in the protection device. In a linear Surge Stopper, the power capability is determined by the size of the pass MOSFET, while in a switching Surge Stopper the power capability is determined by conversion efficiency. Due to its lower power loss, a switching Surge Stopper can operate through longer input voltage surges at higher output current. Under normal operation, an LTC7860 based design also provides an inherent LC EMI filter.