3 Driving the Hot-Swap FETs

For 800V_DC systems, the main choice for the power FET is either 1.2kV drain-to-source voltage (V_DS) rated silicon carbide (SiC) or SiC-cascoded junction FETs. SiC FETs require an 18V gate drive to fully enhance the FET for lowest ON-resistance; SiC-cascoded junction FETs require a 12V gate drive. In a hot-swap application, the FETs typically operate in linear mode during the inrush current-limiting phase. It is important to design the hot-swap circuit appropriately to keep the SOA stress during the inrush phase within the FET's SOA limits. Protecting the FET during fault scenarios such as a power-up into an output short circuit also requires protection schemes. Overload protection cannot put the switch in an active mode because that leads to rapid overheating.

The LMI800PS's configurable gate-drive feature and lower power-limit thresholds (down to 200W) with configurable timers enable flexibility for system designers to develop a reliable hot-swap solution.