ZHCSH69 December 2017 TPS40345
PRODUCTION DATA.
The selection of the output capacitor is typically driven by the output transient response. Equation 5 and Equation 6 overestimate the voltage deviation to account for delays in the loop bandwidth and can be used to determine the required output capacitance.
If VIN(min) > 2 × VOUT, use overshoot (Equation 5) to calculate minimum output capacitance. If VIN(min) < 2 × VOUT, use undershoot (Equation 6) to calculate minimum output capacitance.
With a minimum capacitance, the maximum allowable ESR is determined by the maximum ripple voltage and is approximated by Equation 8.
Two 47-µF and one 220-µF capacitors are selected to provide more than 250 µF of minimum capacitance and 5.2 mΩ of ESR.