3-terminal capacitors as bypass capacitor

Question

The bypass capacitors are used for example to filter out noise at the power supply of an IC. Usually 2 or more capacitors are applied in parallel to cover wider range of frequencies.

However, I have learned about 3-terminal capacitors that have extremely low ESL and therefore cover much wider range of frequencies than usual by pass caps. As I see it, instead of several bypass capacitors one cold use single 3-terminal capacitor. However, since I had never seen the 3-terminal capacitors in such role, I assume there are pitfalls that I am not aware of. What are they?

And what the 3-terminal caps are used for then?

Answer 1

instead of several bypass capacitors one cold use single 3-terminal capacitor.

In fact, Murata recommends them for exactly that application:

However you might find that, due to using more vias per capacitor, these parts take up more board space than you expect.

Also, you will be locked in to buying a fairly high-priced from Murata, rather than a commodity part you can shop around for.

Answer 2

I'd advise avoiding the use of such combination capacitors for the purpose you described. They are best used to save some space in cases where identical capacitor types are needed. For example, if you were building a "brute force" DC power supply with a "Pi" filter, and needed two similar caps with an inductor bridging the two.

The reason for multiple capacitors in the kind of circuit you described is usually to use different types of capacitors, each one doing the job they individually do best. A simple example might be a 500uF electrolytic capacitor in parallel with a 0.1 uF ceramic disc capacitor. The ceramic disk cap will respond much more quickly to fast transients, while the larger electrolytic would provide better filtering of slower supply ripple. While you might get one dual capacitor with different values, I've not seen any in which the two elements are of completely different dielectric types. They may exist for just the purpose I described, but I suspect you'd find the "old fashioned" way of using separate caps to be a cheaper solution.