Original question:
Tool/software:
The main concern is whether the energy dissipated from the soft start capacitor Cff to the ESD diode on the FB pin, i.e., whether the ESD diode could handle when the capacitor discharges. Can any clarification be provided on this point?
Vin = 16V
Vout = 15V
C78 originally 0.001uF
C78 changed to 0.1uF
Respectfully,
-Kevin
Hi Kevin,
Since this is a condition that happens during turn off, it's actually a very easy simulation to set up and run. Shown below is the feedback network and the minimum Cout. The 15 ohm resistor represents the minimum resistive load for this 1A LDO at 15V output. Depending on your Cff value, Rload and Cout, you may or may not have an issue here (but based on some quick simulations, it does not look like it to me). The negative transient with 100nF only gets us halfway to the abs max condition of -7V. If you are operating with more than 10uF on the load then this is even less of an issue. The only way I see an issue is if you increase the feedback divider resistors by an order of magnitude or more, while operating with minimum Cout.
Thanks,
Stephen
