The UCC21732 initiates a fast 2-level turn-off when the overcurrent and short circuit protection is triggered. When the overcurrent and short circuit fault happens, the power power semiconductor transits from the linear region to the saturation region very fast. The channel current is controlled by the gate voltage. By pulling down the gate voltage to a mid-voltage level V2LOFF and stay for a fixed time t2LOFF, the channel current can be limited to a much lower level, which significantly reduces the energy dissipation during the fault event. After t2LOFF, the driver continues to pull down the gate voltage by the soft turn off current ITL3 until it reaches VEE. With dI/dt of the channel current is controlled by the gate voltage and decreasing in a soft manner, thus the overshoot of the power semiconductor is limited and prevents the overvoltage breakdown. The timing diagram of 2-level turn-off shows in Figure 6-10.

Figure 7-6 2-Level Turn-Off