Figure 2-11 and Figure 2-12 show the start-up waveforms for the TPS54334EVM-722. In Figure 2-11, the output voltage ramps up as soon as the input voltage reaches the UVLO threshold as set by the R1and R2 resistor divider network. In Figure 2-12, the input voltage is initially applied and the output is inhibited by using a jumper at JP1 to tie EN to GND. When the jumper is removed, EN is released. When the EN voltage reaches the enable-threshold voltage, the start-up sequence begins and the output voltage ramps up to the externally set value of 3.3 V. The input voltage for these plots is 12 V and the load is 5 Ω.

Figure 2-11 TPS54334EVM-722 Startup Relative to V_IN

Figure 2-12 TPS54334EVM-722 Startup Relative to Enable