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2.8 Input Voltage Ripple
The TPS54231EVM-372 input voltage ripple is shown in Figure 2-8 . The output current is the rated full load of 2
A and V
IN
= 15 V. The ripple voltage is measured directly across the input capacitors.
Figure 2-8. TPS54231EVM-372 Input Ripple
2.9 Powering Up
The start-up waveforms are shown in Figure 2-9 and Figure 2-10 . In Figure 2-9 , the top trace shows V
IN
, and
the bottom trace shows V
OUT
. In Figure 2-10 , the top trace shows EN (enable) whereas the bottom trace shows
V
OUT
. In Figure 2-10 , the input voltage is initially applied and the output is inhibited by using a jumper at J2 to tie
EN to GND. When the jumper is removed, EN is released. When the EN voltage reaches the enable-threshold
voltage of 1.25 V, the start-up sequence begins and the internal reference voltage begins to ramp up at the
internally set rate toward 0.8 V and the output voltage ramps up to the externally set value of 3.3 V. The input
voltage for these plots is 15 V and there is no load.
Figure 2-9. TPS54231EVM-372 Start-Up Relative to V
IN
Test Setup and Results www.ti.com
8 TPS54231 Step-Down Converter Evaluation Module User's Guide SLVU263A – AUGUST 2008 – REVISED OCTOBER 2021
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