First of all I'd like to say that I'm quite new in electronics (I'm a software developer) so I might be missing some basic knowledge for which I apologize.

I'm trying to create a DAC using the PCM5122. The datasheet mentions that the charge pump flying capacitor should be a 2.2uF COG Ceramics (I'm guessing COG should be C0G - C zero G).

Now, I've been to my local electronics dealer and he has never heard of a ceramic capacitor with that value. Also Conrad (where I usually get my stuff) doesn't have one. The only place where I can find such a capacitor (SMD) is at Mouser (which will cost me € 20,- on shipping).

My questions are:

  • Why is this so rare?
  • Is there a non-SMD variant of this capacitor (I can't find one but maybe I'm not using the correct search terms)?
  • Can I use something else in stead?

I'm guessing you are looking out the "Layout Example" section, where the data sheet has a couple of problems, which you have found! First, there is no reason for an NPO or COG capacitor on the charge pump; a 2.2 uF X7R will be fine here, since the charge pump is not in the audio circuit. COG caps are only required on the output filter to prevent the filter roll-off from moving around with temperature. Second, the output filter cap values (which should be NP0) are recommended to be 2.2 nF (much easier to find), not 2.2 uF. This is mentioned several places elsewhere in the document. The "Layout Example" is a typo. Good luck!


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