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I am using a switching voltage regulator to go from 5V to 3.3V, 1A of output current. The datasheet specifies 22uF ceramic capacitors for the input and output. Can I use 2 10uF capacitors instead of one 22uF capacitor?

Besides the difference in frequency response (10uF has a higher resonant frequency), is there a reason why one 22uF would be better than using two 10uF?

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  • \$\begingroup\$ Normally, that would be ok. 22 uF ceramic? Or electrolytic? \$\endgroup\$ – Mike Waters Jan 12 '17 at 0:43
  • \$\begingroup\$ Its close enough so you should be OK. Keep the two caps electrically close together. And since it is a switcher, remember to pay attention to the type of capacitor the manufacturer recommends. The wrong type of capacitor could effect the longevity and reliability of the circuit more than the 2uF difference from the recommended value. \$\endgroup\$ – Randy Jan 12 '17 at 0:44
  • \$\begingroup\$ @MikeWaters, it specifies "Low ESR Ceramic (MLCC)". \$\endgroup\$ – Adam B Jan 12 '17 at 0:50
  • \$\begingroup\$ @AdamB To get a really concrete answer, please post the part numbers for: your switching voltage regulator, the 22uF capacitor, the 10uF capacitor. \$\endgroup\$ – Nick Alexeev Jan 12 '17 at 1:11
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Two is usually better than one for ceramic.

In a non-electrolytic capacitor and electrolytic capacitors with solid electrolyte the metallic resistance of the leads and electrodes and losses in the dielectric cause the ESR. Typically quoted values of ESR for ceramic capacitors are between 0.01 and 0.1 ohms. ESR of non-electrolytic capacitors tends to be fairly stable over time; for most purposes real non-electrolytic capacitors can be treated as ideal components. (Wikipedia on ESR)

The ESR for the capacitors are limited by the manufacturing process and related more to physical size than value. Depending on the type of capacitor being used, the ESR of two in parallel will be less than a single capacitor of twice the value.

If you look at this Murata catalog you will see that the ESR is defined for a range of physical sizes rather than per capacitance value.

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Two 10uF would probably be better, due to them likely having lower ESR or equivalent series resistance. If it calls for ceramic, stick to ceramic. Don't change type of capacitor, as the different types can have drastically different ESR. The only reason one 22uF would be better is because there is one less component to place on the PCB and might cost slightly less.

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  • \$\begingroup\$ Thanks! The datasheet specifies "Low ESR Ceramics". The 22uF are 9x more expensive (probably due to the size), so using 2 10uF seems like a better option. \$\endgroup\$ – Adam B Jan 12 '17 at 0:49
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    \$\begingroup\$ Yes, the very high capacitance ceramic caps in a small package can get very expensive since it's pushing the limits of the technology. I also use several parallel caps when I need low profile height. \$\endgroup\$ – Vince Patron Jan 12 '17 at 0:57
  • \$\begingroup\$ Yes the larger value ceramics can get more expensive, however consider the larger footprint of two components, the added cost of a second component, and setup/tooling and placement fees for automated assembly. It probably would be less overall for two components, but due dilligence is a good idea here. PS make sure the cap's voltage rating is double the maximum peak ripple voltage (and don't overshoot RMS current) for best reliability. \$\endgroup\$ – rdtsc Jan 12 '17 at 12:19

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