8.2.1.4 Output Capacitor

The output capacitor is selected based upon the desired output ripple and transient response. The initial current of a load transient is provided mainly by the output capacitor. The output ripple of the converter is:

Equation 12.

When using MLCCs, the ESR is typically so low that the capacitive ripple may dominate. When this occurs, the output ripple will be approximately sinusoidal and 90° phase shifted from the switching action. Given the availability and quality of MLCCs and the expected output voltage of designs using the LMR10530, there is really no need to review any other capacitor technologies. Another benefit of ceramic capacitors is their ability to bypass high frequency noise. A certain amount of switching edge noise will couple through parasitic capacitances in the inductor to the output. A ceramic capacitor will bypass this noise while a tantalum will not. Since the output capacitor is one of the two external components that control the stability of the regulator control loop, most applications will require a minimum of 22-µF output capacitance. In the case of low output voltage, a larger output capacitance is required to ensure sufficient phase margin. Capacitance can often, but not always, be increased significantly with little detriment to the regulator stability. Like the input capacitor, recommended multilayer ceramic capacitors are X7R or X5R types. Again, verify actual capacitance at the desired operating voltage and temperature. Check the RMS current rating of the capacitor. The maximum RMS current rating of the capacitor is:

Equation 13.

One may select a 1206 size MLCC for output capacitor, since its current rating is typically above 1 A, more than enough for the requirement.