9.2.2.1.2 Output Capacitor Selection

The advanced fast-response voltage-mode control scheme of the TPS6224X-Q1 device allows the use of tiny ceramic capacitors. Ceramic capacitors with low-ESR values have the lowest-output voltage ripple and are recommended. The output capacitor requires either an X7R or X5R dielectric. Y5V and Z5U dielectric capacitors, aside from their wide variation in capacitance over temperature, become resistive at high frequencies.

At nominal load current, the device operates in PWM mode and the RMS ripple current is calculated as in Equation 4:

Equation 4.

At nominal load current, the device operates in PWM mode and the overall output voltage ripple is the sum of the voltage spike caused by the output capacitor ESR plus the voltage ripple caused by charging and discharging the output capacitor as in Equation 5:

Equation 5.

At light load currents, the converter operates in power save mode and the output voltage ripple depends on the output capacitor and inductor value. Larger output capacitor and inductor values minimize the voltage ripple in PFM mode and tighten DC output accuracy in PFM mode.