Use Equation 38 to estimate the output capacitance required to manage the
output voltage overshoot during a load-off transient (from full load to no load)
assuming 10% overshoot is allowed.
Equation 38.
Noting the voltage coefficient of ceramic
capacitors where the effective capacitance decreases significantly with applied
voltage, select four 10µF, 25V, X7R ceramic output capacitors, and one 100µF,
35V, hybrid aluminum polymer capacitor. Generally, when sufficient capacitance
is used to satisfy the load-off transient response requirement, the voltage
undershoot during a no-load to full-load transient is also satisfactory.
Use Equation 39 to estimate the peak-peak output voltage ripple at nominal input voltage.
Equation 39.
where
RESR is the
effective equivalent series resistance (ESR) of the output
capacitors.
128µF is the total
effective (derated) ceramic output capacitance at 6V.
Use Equation 40 to calculate the output capacitor RMS ripple current and verify that the
ripple current is within the capacitor ripple current rating.