1
\$\begingroup\$

In a project, I am using the PTN78020H power supply, and it has a recommended circuit (from the datasheet linked above) that looks like this: Circuit diagram for power supply

Now on the input, it requests a massive 4 x 4.7uF ceramic capacitors. I've had a look around and haven't found any place selling through whole ceramic capacitors in values anywhere near that.

Typically a ceramic cap is used to filter high frequencies, and electrolytic have much worse performance, so I don't want to switch all the input caps to electrolytic, but would it be feasible to, say, use 10uF electrolytic and 1uF ceramic? Tantalum caps come in the 4.7uF capacitance range, and I believe have better performance than electrolytic?

My question is pretty much: Assuming I can't get hold of 4.7uF ceramic capacitors, what should I do?

\$\endgroup\$
  • 4
    \$\begingroup\$ Mouser lists 1,339 part numbers for ceramic 4.7 uF capacitors. At least the first 5 pages are through-hole. This is not an outrageously large value nowadays. \$\endgroup\$ – The Photon May 27 '16 at 3:05
  • \$\begingroup\$ You will most likely find them in a smd package, not in a disc package. Such high values are becoming more common as industry shifts toward more smd packages and less through-hole. The schematic implies that the best ESR performance is with what they show. Keep the leads for Co short. \$\endgroup\$ – Sparky256 May 27 '16 at 3:26
  • \$\begingroup\$ @Sparky256 -- modern THT ceramics are available in such values -- but they're monolithics not discs. (i.e. they're a SMT cap with leads soldered on ;) \$\endgroup\$ – ThreePhaseEel May 27 '16 at 4:30
  • \$\begingroup\$ Five 1uF ceramic mlcc in parallel won't do the work? \$\endgroup\$ – soosai steven May 28 '16 at 4:05
6
\$\begingroup\$

Your assumption is incorrect. 4.7 uF ceramic capacitors are widely available. Mouser, the same site where you seem to have found your power supply, has on the order of 100 listings for through hole 4.7 uF ceramic capacitors, and over 1000 for SMT.

So the best thing to do would be to simply purchase 4.7 uF ceramic capacitors, as recommended by the datasheet of your power supply.

\$\endgroup\$
  • \$\begingroup\$ For what it's worth, they also list a 120 uF ceramic radial-leaded part, although its price might give you a shock. \$\endgroup\$ – The Photon May 27 '16 at 3:32

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.