The LTC7860 is a high efficiency switching surge stopper with overvoltage and overcurrent protection for high availability systems. During normal operation the LTC7860 turns on an external P-channel MOSFET continuously (100% duty cycle) to pass the input voltage through 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. Note that under normal operation an LTC7860 based design also provides an inherent L-C EMI filter. The LTC7860 builds on Linear Technology’s popular linear surge stoppers such as the LT4363 by offering high efficiency switching protection to extend output current capability and reduce power loss during transients and faults. 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 low power loss, a switching surge stopper can operate through longer input voltage surges at higher output current than a linear solution.