UCC33420 pre-production samples have the following operating limits. Production devices will have these limitations removed.

1. For ambient operating temperature < 0°C, the following sequence is required to allow the device reach regulation point during start-up. EN/FLT pin required to be high (V_EN/FLT > V_{EN_R} ) before applying input voltage VINP to the device. This can be achieved by connecting EN/FLT pin after the 18kΩ resistor directly to the VINP pin and applying VINP with rise time > 6ms on the device.
2. For ambient operating temperature < 0°C, the following protection features; short-circuit, UVP and OVP protections of VCC output are disabled. Fault reporting and auto-restart features due to these faults will be disabled as well. If the part shuts down as a result of fault condition, the part will require to follow the same condition in step 1 above to restart and reach regulation. This require to recycle VINP by falling below V_{VINP_UVLO_F} and then rising above V_{VINP_UVLO_R} with the same > 6ms rise time.