Safely use trench MOSFETs on hot swap application by determining its operation within its SOA in a limited time, app note from International Rectifier. Link here (PDF)
Hot Swap circuits are used to allow for “Hot Plugging” of circuit boards into back planes. The applications that require such functionality are mission critical, such as servers and communications equipment that must operate continuously. These circuit boards are usually employed in a rack mount system which consists of an array of boards that cannot be powered down. Thus hot swapping allows for a bad board in the array to be replaced without powering down the entire system.
In essence the Hot Swap circuit, which is between the board input rail and the rest of the board’s circuitry, is an inrush current limiter that allows for charging of the bulk capacitance in a controlled manner. Also faults, such as over current and overvoltage are managed by Hot Swap circuits.