After a short-circuit event is detected, the SiC MOSFET needs to be turned off safely to minimize damage to the system.

Parasitic inductances can interact with fast I_D switching to induce voltage $(V=L\times \frac{di}{dt})$ across the SiC MOSFET. Under nominal events where I_D is within the rated limits, using normal turn-off induces voltage that is within limits of the SiC MOSFET. However, during short-circuit events, the induced voltage can reach catastrophic levels that can destroy the SiC MOSFET.

Soft turn-off is a design that increases the turn-off time, which consequently reduces the switching speed when turning off the SiC MOSFET. This decreases di/dt to minimize the induced voltage. Figure 3-5 shows a plot illustrating how OUT turns off slowly when short-circuit is detected via DESAT protection in UCC5710x. Other conceptual timing characteristics related to DESAT protection are included in the diagram: t_DESLEB (leading edge blanking time to prevent false trigger from SiC MOSFET turn-on transient), t_DESFIL (deglitch filter time to prevent false trigger from noise while SiC MOSFET is on), t_DES2OUT (time between reaching DESAT threshold and OUT falling to 90%), t_DES2FLT (time between reaching DESAT threshold and FLT falling).