Selecting decoupling capacitor.

[Naveen G Bhat]

Dear forum,
I wanted to know how we should select decoupling capacitor for power supply design?
in some case these details are available in datasheet i will use same parameter,same value decoupling capacitors.
in some other cases they don't specify the decoupling capacitor values, then how i should calculate or is there any ideal decoupling values for power supply design??

[robertferanec]

Power design and analysis is a whole big part of electronics design. Generally you really would like to follow design guides or reference designs. If you are creating completely new circuit and you would like to be sure, you may need to calculate it and/or simulate it.

Generally, for standard digital designs you will find 100nF capacitors placed close to each power supply pin (but value depends on frequencies which are used in the board, for example often you can find there also 10nF, 200nF, etc). Then usually in a group of smaller caps you will find one bigger cap (e.g. 10uF, 2.2uF) and often you also may want to use Ferrite BEADs which are used together with the bigger cap as a filter.

Sometimes what can be useful are filter calculators from manufacturers like Murrata, just an example here: https://www.murata.com/en-us/tool/download/emc