High Power Hot Swap with Power Sharing and Digital Telemetry

Hot Swap circuits are increasingly being used at power levels above 1000W. At these power levels multiple switch MOSFETs are required, but adding MOSFETs does not improve the power dissipation capability of the circuit when the current is regulated because the MOSFETs don’t inherently share current. The LTC4282 addresses this problem by dividing the MOSFETs into two parallel banks with independent current limits that enforce sharing between the two banks. This method doubles the SOA of an application while using the same number and type of MOSFETs of a traditional solution, allowing the use of less expensive MOSFETs with lower SOA. The LTC4282 is also capable of two staged architectures, where the RDS-ON and power dissipation requirements of the hot-swap switch are separated into two banks of MOSFETs, allowing the use of MOSFETs optimized to those purposes, rather than trying to find a single MOSFET that does both. Hot-swap applications are used at the power input to a board, so it is a natural location at which to monitor power consumption, and other telemetry information. The LTC4282 uses a pair of 12-bit data converters to continuously monitor output current and voltage. From that power and energy are calculated on chip. Peak detectors store minimum and maximum readings, and digital window comparators produce system alerts at desired thresholds. Also included on the LTC4282 is an on-chip EEPROM which allows the part to autonomously configure itself at power-up for any application. The EEPROM is also used for fault logging, general purpose non-volatile data and history storage, and can disable the hot-swap on a failed board to prevent it from attempting to power-up if it is removed and re-inserted. The LTC4282 is the only IC on the market with non-volatile memory and also the only IC on the market that is made specifically to control two groups of MOSFETs in a single hot-swap application.