STPM801 Hot Swap Voltage Controller STMicroelectronics STPM801 Hot Swap Voltage Controller provides integrated hot swap, soft start, and o-ring protections. These protections prevent loads from high-voltage transients, limiting and regulating the output during an overvoltage event. These include load dumps by controlling the voltage drop across an external N-channel MOSFET. The device additionally monitors the input supply to protect it in case of overvoltage (OV) and undervoltage (UV) conditions.