Ripple Current of Capacitor in design consideration

In the datasheet for a capacitor, you’ll often find a ‘Ripple Current’ specification. Does this specification have any impact on our product design?

The ripple current (I) is the AC current flowing through the capacitor. Since there is an internal resistance (ESR) in the capacitor, ripple current will generate heat (P) to affect the capacitor life and function. Too much heat may damage the capacitor by exceeding its maximum permitted core temperature.

  • P = I² x ESR

Since ripple current varies with AC voltage frequency, the ripple current value in the specification is just a reference. Please note that different manufactures use their own specific testing conditions and criteria - one manufacturer tests their parts under 100kHz while another manufacturer tests their parts under 120kHz.

If you’re concerned with ripple current, check a ripple current graph if the manufacturer supplies one, or work backwards from their given ripple and ESR numbers to determine the maximum ‘P’ value the capacitor can handle.