Decoupling capacitors

[CommanderLake]

Can I use a 10µF ceramic instead of a 10µF electrolytic and 0.1µF film with an LM3886 to save space?

 

[davenn]

you need the 0.1uF
it isn't the same as a 10uF
not sure what you are referring to as a 10uF ceramic ? I have never seen a 10uF ceramic

Dave

 

[CommanderLake]

http://uk.farnell.com/tdk/c3216x5r1h106k160ab/cap-mlcc-x5r-10uf-50v-1206/dp/2346951
Surely the low ESR of a 10µF ceramic will take care of the high frequency ripples?

 

[KrisBlueNZ]

I would always use what the data sheet recommends, unless I thought I knew more than the authors of the data sheet!

 

[CommanderLake]

I've just tested the volt drop of various electrolytics, film and ceramic capacitors with my USB oscilloscope, a 3.8v battery source and a 10 ohm load and the results are as follows:

With no capacitor there are wild peaks and dips when the load is applied.

Aluminium electrolytics remove noise and wild peaks and drops when the load is applied but dont slow the immediate volt drop.

Film and ceramic eliminate the sudden volt drop and smooth it to a gentle slope, smaller values dip slightly before stabilizing.

A larger aluminium electrolytic along side a smaller film capacitor doesnt do much at all, if anything its more stable without the electrolytic.

 

[Arouse1973]

you need the 0.1uF
it isn't the same as a 10uF
not sure what you are referring to as a 10uF ceramic ? I have never seen a 10uF ceramic

Dave

I use 10uF ceramics as standard PDS support on most of my designs now. I even use some 100uF ceramics for certain applications. For the 100uF I limit the working voltage to about 6.3V, otherwise they get very expensive.

Adam

 

[Arouse1973]

http://uk.farnell.com/tdk/c3216x5r1h106k160ab/cap-mlcc-x5r-10uf-50v-1206/dp/2346951
Surely the low ESR of a 10µF ceramic will take care of the high frequency ripples?

It's the ESL that dominates at high frequency because the ESR is normally very low with ceramics anyway.
Adam