SNVS690I January 2011 – August 2021 LMZ14201H
The ESR of the output capacitor affects the output voltage ripple. High ESR will result in larger VOUT peak-to-peak ripple voltage. Furthermore, high output voltage ripple caused by excessive ESR can trigger the overvoltage protection monitored at the FB pin. The ESR should be chosen to satisfy the maximum desired VOUT peak-to-peak ripple voltage and to avoid overvoltage protection during normal operation. The following equations can be used:
As worst-case, assume the gain of AFB with the CFF capacitor at the switching frequency is 1.
The selected capacitor should have sufficient voltage and RMS current rating. The RMS current through the output capacitor is: