The Benefits of MLCC Capacitors Part I

Casual observation would claim that the main job of a parts search engine like OEMsecrets involves…

Casual observation would claim that the main job of a parts search engine like OEMsecrets involves finding cheaper sources for expensive parts. Recently, relatively low-priced MLCC capacitors have taken the lead in terms of search interest – let us tell you what this means for your daily work as a designer…

First of all…

Electrolytic capacitors are not the most desirable of products; they are heavy, large, and tend to fail early. Just a quick look at the various test equipment repair forums returns stories about expensive pieces of gear which croaked because some electrolytic capacitor decided to belch out it’s electrolyte.

Some years ago, a designer at a third-class German electronics trade show introduced the idea of trying to go electrolyte capacitor free. This can be achieved in two ways; firstly, by replacing classics such as the LM2576 with a higher frequency part such as the ACT4065 – they are not only cheaper, but also permit the use of smaller coils and smaller filtering capacitors. Remaining filtering capacitors which are still required are then chosen from MLCC families, paralleling multiple ones if necessary.

The inductor used for a 52KhZ switching regulator is much much bigger…

…than it’s counterpart on the 210KhZ design.

At first glance, opting for MLCC is a miracle. Let us compare the GRM21BR61A106KE19L to an electrolytic capacitor from a well known brand – by going through hole or by switching to a lesser brand, the electrolytic capacitor would of course become a bit cheaper…

 
Part GRM21BR61A106KE19L RNU1A100MDS1
Type MLCC, 10uF 10V Elco, 10V 10uF
Dimensions 0805 4mmx5mm, Throughhole
Weight 9.5mg Not published, similar part weighs 480mg with leads
Price, Q1 24 €-cent 35 €-cent
 

Taking a look at the actual specifications of the capacitor reveals the situation to be less rosy. The figure, taken directly from Murata’s datasheet, shows that the capacitance of the component decreases significantly as the applied voltage raises.

Actually getting this information can be tricky; whilst first-rate vendors usually provide this data themselves, designers working with cheaper parts can often find themselves forced having all oscilloscope and using the good old RC discharge curve to find out more.

As if this was not enough…

Recent news stories also point to shortages in the MLCC capacitor supply chain. Most distributors now provide warnings about manufacturing delays, with some parts having lead times of up to 38 weeks.

Whilst this might not be a problem for a large vendor such as Apple or Samsung, a smaller company with small order volumes will likely find itself on the short end of the stick if push comes to shove.

In short, MLCC capacitors do provide benefits, but are not a silver bullet for all capacitor-related problems. Tune in soon for the second part of our story, which looks at the various ways designers can handle the stock shortages in the MLCC capacitor market using OEMsecrets tools and a bit of ingenuity.

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