Datasheet
2.9 Powering Up
V
OUT
V
IN
SS/ENA
V
OUT
1V/div
500mV/div
2.10 Thermal Characteristics
Test Setup and Results
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The start-up waveforms are shown in Figure 8 and Figure 9 . In Figure 8 , the top trace shows V
IN
, and the
bottom trace shows V
OUT
. In Figure 9 , the top trace shows EN (enable) whereas the bottom trace shows
V
OUT
. In Figure 9 , 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 8. TPS54917EVM-367 Start-Up Relative to V
IN
Figure 9. TPS54917EVM-367 Start-up Relative to Enable
This section shows a thermal image of the TPS54917EVM-367 running at 3.3 V input and 9 A load. These
are the worst case conditions for maximum power loss. There is no air flow and the ambient temperature
is 25 ° C. The peak temperature of the IC (85.8 ° C) is well below the maximum recommended operating
condition listed in the datasheet of 150 ° C.
8 TPS54917EVM-367 9-A, SWIFT™ Regulator Evaluation Module SLVU278 – December 2008
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