The MAX4505 is a single signal-line protector featuring a fault-protected input and rail-to-rail signal handling capability. The input is protected from overvoltage faults up to ±36V with power on or ±40V with power off. During a fault condition, the input terminal becomes an open circuit and only nanoamperes of leakage current flow from the source, while the switch output (AOUT) furnishes typically 19mA from the appropriate polarity supply to the load. This ensures an unambiguous rail-to-rail output when a fault begins and ends.The MAX4505 protects both unipolar and bipolar analog signals using either unipolar (+9V to +36V) or bipolar (±8V to ±18V) power supplies. The device has no logic control inputs; the protector is always on when the supplies are on. On-resistance is 100Ω max, and on-leakage is less than 0.5nA at TA= +25°C. The MAX4505 is available in 5-pin SOT23 and 8-pin µMAX® packages.ApplicationsAutomated Test Equipment (ATE)Data AcquisitionHot-Insertion Boards/SystemsProcess Control SystemsRedundant/Backup SystemsSensitive Instruments