Datasheet

Time - 100 µs/div
1 V/div
G014
200 mV /div
1 A/div
V Falling/div
OUT
V /div
IN
I , Inverted
OUT
for Clarity
Time - 100 µs/div
1 V/div
G013
200 mV /div
1 A/div
V Falling/div
OUT
V /div
IN
I , Inverted
OUT
for Clarity
Test Setup and Results www.ti.com
2.10 Powering Down
Figure 14 and Figure 15 show the shut down waveforms for the EVM. In Figure 14, the output voltage
ramps down as soon as the input voltage falls below the UVLO stop threshold as set by the R1 and R2
resistor divider network. At the point of shutdown, the input voltage rises slightly due to the resistive drop
in the input feed impedance. In Figure 15, the output is inhibited by using a jumper at JP1 to tie EN to
GND.
Figure 14. TPS54678EVM-155 Shut-down Relative to V
IN
Figure 15. TPS54678EVM-155 Shut-down Relative to EN
2.11 Hiccup Mode Current Limit
The TPS54678 has hiccup mode current limit. When the peak switch current exceeds the current limit
threshold, the device shuts down and restarts. Hiccup mode current limit operation is shown in Figure 16
and Figure 17. Figure 16 shows the activation of hiccup mode current limit. When the peak current limit is
exceeded, the output voltage is disabled. Figure 17 shows the operation of the TPS54678 with the output
shorted to ground. The device will continuously reset until the fault condition is removed.
12
TPS54678EVM-155 6-A, SWIFT™ Regulator Evaluation Module SLVU747–June 2012
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