SLVUCE3 april 2023 TPS54KB20
Figure 3-17 and Figure 3-18 show the start-up and shutdown waveforms for U2 with EN. In Figure 3-17, the input voltage is initially applied and the output is inhibited by pulling EN to GND using an external function generator. When the EN voltage is increased above the enable-threshold voltage, the start-up sequence begins and the output voltage ramps up to the externally set value. In Figure 3-18, the external function generator pulls EN to ground and the TPS54KB20 shuts down.