Datasheet

Start-Up
2-7
Test Setup and Results
2.9 Start-Up
The start-up voltage waveform of the TPS54314EVM, with C1 left open, is
shown in Figure 2–10. In Figure 2–10, the input voltage is displayed on
channel 3, the output voltage is displayed on channel 1, and the power good
signal is displayed on channel 2. Once the input voltage rises above the 2.9-V
start-up threshold, the output voltage begins to rise linearly to 1.8 V in 3.6 ms.
Once the output voltage has reached its final value, the open-drain power
good signal rises to a high state. The start-up time can be extended by using
an external slow start capacitor, C1. To program a specific slow start time, see
section 1.3.4 Slow Start. The shorting jumper on J2 should not be used to
enable the EVM. Using the J2 jumper may cause excessive voltage transients
on the SS/ENA pin. Use an external enable signal, instead of J2 jumper.
Figure 2–10. Measured Start-Up Waveforms
V
I
= 2 V/div
V
O
= 1 V/div
V
(PWRGD)
= 1 V/div
2 ms/div