Datasheet

Start-Up
2-12
Figure 2–14. Measured Start-Up Waveform, Four Diode Precharge
V
I
500 mV/div
Time Scale 5 ms/div
V
O
500 mV/div
Figure 2–15 shows the start-up waveform with the output precharged through
4 diodes and no load. Compare the precharge level to that in Figure 2–14 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 2–15 is very close to the final output value.
This would be the case if less than four diodes were used.
Warning
The precharge level must never exceed the output set point under
any line or load condition for proper circuit operation.