Texas Instruments TPS54673EVM-225, User Manual, Page: 30 / 42

Start-Up
2-14
Figure 2–18. Measured Start-Up Waveform, TPS54373 With Precharge
VI 1 V/div
Time Scale – 5
µ
s/div
VO 1 V/div
Figure 2–20 shows the start-up waveform with the output precharged and no
load. Compare the precharge level to that in Figure 2–18 to see how start-up
load current affects the voltage drop across the diodes and the final precharge
voltage. As in the previous example, when the internal reference exceeds the
voltage fed back to the VSENSE pin, the output begins to ramp up to its final
preset value at the slow-start rate. It is important to note how the precharge
level in Figure 2–19 is very close to the final output value. The precharge level
must never exceed the output set point under any line or load condition for
proper circuit operation.
Figure 2–19. Measured Start-Up Waveform, TPS54673 With Precharge and No Load
VI 1 V/div
Time Scale – 5
µ
s/div
VO 1 V/div