The MAX4959/MAX4960 overvoltage protection controllers protect low-voltage systems against high-voltage faults of up to +28V. When the input voltage exceeds the overvoltage lockout (OVLO) threshold, these devices turn off an external pFET to prevent damage to the protected components. The undervoltage lockout (UVLO) threshold holds the external pFET off until the input voltage rises to the correct level. An additional safety feature latches off the pFET when an incorrect low-power adapter is plugged in. The MAX4959/MAX4960 control an external battery switchover pFET (P2) (see Figures 4 and 6) that switches in the battery when the AC adapter is unplugged. The undervoltage and overvoltage trip levels can be adjusted with external resistors.