The FLT pin of the UCC21732 is open drain and can report a fault signal to the DSP/MCU when the overcurrent and short circuit fault is detected through OC pin. The FLT pin is pulled down to GND, and is held in low state unless a reset signal is received from RST/EN. The device has a fault mute time t_FLTMUTE, within which the device ignores any reset signal.

The RST/EN is pulled down internally. The device is disabled by default if the RST/EN pin is floating. The pin has two purposes:

• Resets the overcurrent and short circuit fault signaled on FLT pin. The RST/EN pin is active low, if the pin is set and held in low state for more than t_RSTFIL, the fault signal is reset and FLT is reset back to the high impedance status at the rising edge of RST/EN pin.
• Enable and shutdown the device. If the RST/EN pin is pulled low, the driver is disabled and shut down by the regular turn off. The pin must be pulled up externally to enable the part, otherwise the device is disabled by default.