Hello Matsumoto-san,
Wilson is correct. This is simply a power decoupling capacitor to help keep the voltage to the device stable in cases where the device may get loaded quickly.
There is not necessarily a cut and dry method of determining cap size. It really depends on what the loading conditions are and what kind of ripple you are willing to accept on the device. Bigger will help to reduce ripple due to transients, but 0.1 to 1uF should be plenty. You shouldn't need something like a 22uF capacitor.
Best,
Michael
Wilson is correct. This is simply a power decoupling capacitor to help keep the voltage to the device stable in cases where the device may get loaded quickly.
There is not necessarily a cut and dry method of determining cap size. It really depends on what the loading conditions are and what kind of ripple you are willing to accept on the device. Bigger will help to reduce ripple due to transients, but 0.1 to 1uF should be plenty. You shouldn't need something like a 22uF capacitor.
Best,
Michael