SBVS343A March 2019 – September 2019 TPS7A78
Equation 8 yields a capacitance value of 153 nF, as given by Equation 9, which results from the VAC (MIN) voltage and frequency of this application. This value is for the FB configuration. For the HB configuration, doubling the calculated capacitance value yields 306 nF, and approximate this value up to the nearest standard capacitor value, which yields a CS value of 330 nF.
As mentioned in the Calculating the Cap-Drop Capacitor CS and Input and Output Capacitors Requirements sections, capacitance loss under long-term service is inevitable and must be considered in the design. Follow the manufacturer recommendations and guidelines for capacitor derating and degradation over time.