The effective output capacitance can range from 40 μF (minimum) up to 200 μF (maximum) for a single L-C system design. When using a second L-C filter, the first L-C filter must have output capacitance between 40 μF and 80 μF, the second stage L-C filter (if used) must have at least 20 μF of capacitance, and the total capacitance for both L-C filters must be less than 200 μF. Load transient testing and measuring the bode plot are good ways to verify stability.
Ceramic capacitors (X5R or X7R) are recommended. Ceramic capacitors have a DC-Bias effect, which has a strong influence on the final effective capacitance. Choose the right capacitor carefully in combination with considering its package size and voltage rating. The ESR and ESL of the output capacitor are also important considerations in selecting the output capacitors for low noise applications. Smaller package sizes typically have lower ESL and ESR. 0805 or smaller packages are recommended, as long as they provide the required capacitance and voltage rating for stable operation. Table 8-5 lists recommended output capacitors.
|CAPACITOR TYPE||CAPACITOR VALUE||MANUFACTURER||VOLTAGE (V)||PACKAGE|
|Bulk Capacitor||22 μF, X7S||TDK C2012X7S1A226M125AC||10||0805|
|Bulk Capacitor||47 μF, X7R||Murata GRM32ER71A476ME15L||10||1210|