Figure 4-1 and Figure 4-2 show the start-up waveforms for the TPS51397AEVM. In Figure 4-1, the output voltage ramps up as soon as the input voltage reaches the UVLO threshold. In Figure 4-2, the input voltage is initially applied and the output is inhibited by using a jumper at J5 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 5 V. The input voltage for these plots is 12 V and the load is 1 Ω.

Figure 4-1 Start-Up Relative to V_IN, Iout = 5 A

Figure 4-2 Start-Up Relative to Enable, Iout = 5 A