Datasheet

2.9 Powering Up
2.10 Eco-mode™ Operation
www.ti.com Test Setup and Results
The start-up waveforms are shown in Figure 9 . In Figure 9 , the top trace shows V
OUT
, and the bottom
trace shows V
IN
. The input voltage is initially applied, and when the input reaches the undervoltage lockout
threshold, the start-up sequence begins and the output ramps up at the externally set rate toward the
value of 3.3 V. the input voltage for this waveform is 34 V with a 1.5 A load.
Figure 9. TPS54140EVM-429 Start-Up Relative to V
IN
At light load currents, the TPS54140 is designed to operate in pulse skipping Eco-mode™. When the
COMP pin lowers to 500 mV typical, the device enters Eco-mode™ operation.
Figure 10 shows Eco-mode operation, channel 1(C1) shows the output voltage while channel 2(C2) shows
the switching node (PH).
Figure 10. TPS54140EVM–429 Eco–mode™ Operation
SLVU285 – March 2009 TPS54140EVM-429 1.5-A, SWIFT™ Regulator Evaluation Module 9
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