2.2uF C0G/NP0 - Page 1
Forum section: electronics / projects

author: fabiodl
author_rank: Frequent Contributor
timestamp: October 28, 2019, 02:14:11 am
content: I am developing a board around the TI pcm5122.Thedatasheetat page 66 reports that all caps should be 2.2uF C0G.I cannot find any caps with that dielectric/temperature coefficient on Digikey with capacitance over 560nF.Do bigger C0G caps exist? What/Where should I search for?

author: langwadt
author_rank: Super Contributor
timestamp: October 28, 2019, 02:17:20 am
content: use 4?

author: DaJMasta
author_rank: Super Contributor
timestamp: October 28, 2019, 03:18:13 am
content: I'd be sort of surprised if they do, I'm actually surprised you can find a 500nF C0G, the ones I'm used to seeing top out in the single digits.Why not a film cap instead?

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: October 28, 2019, 03:23:33 am
content: Hi,I think is a an error the correct value is 2.2nFThey use 2.2nF in other places in the documentation.2.2nF and 470is 153kHz2.2uF and 470is 153 Hz low pass filter.Jay_Diddy_B

author: duak
author_rank: Super Contributor
timestamp: October 28, 2019, 03:26:59 am
content: Wow, I'm surprised there are even 560 nF parts. I think it's a mistake. The output filter should be 2.2 nF C0G as per the schematic, while the 2.2 uF for the charge pump can be an X7R.Here's a link to someone who thinks the same:https://electronics.stackexchange.com/questions/386216/pcm512x-charge-capacitor-value

author: floobydust
author_rank: Super Contributor
timestamp: October 28, 2019, 03:30:53 am
content: Na, it's several typo's. There are no C0G/NPO's that big and you would not put something so huge at the DAC's outputs.Those are properly 2.2nF C0G?, and 2.2uF X7R are used for the charge-pump. Look at PCM5122 Evaluation Modulehttp://www.ti.com/tool/PCM5122EVM-U

author: BravoV
author_rank: Super Contributor
timestamp: October 28, 2019, 03:38:15 am
content: A 100nF C0G/NPO is about 24 dollars a pop, example ->Kemet C0G CapI can't imagine what will be the price if at 2.2uF.

author: fabiodl
author_rank: Frequent Contributor
timestamp: October 28, 2019, 04:11:05 am
content: Thank you very much everybody.The evaluation board's schematic/bill of materials really helps a lot, it was a typo indeed!

author: exmadscientist
author_rank: Frequent Contributor
timestamp: October 28, 2019, 05:16:51 am
content: Quote from: BravoV on October 28, 2019, 03:38:15 amHuh? No they're not. I've used a bunch of 100nF NP0 caps when I need stability and it's not worth expending more design effort to use something cheaper. They're usually about a quarter, likeGRM31C5C1E104JA01Lat US$0.23 in quantity 100.It also looks like Kemet has recently introduced a new NP0 line that's about a factor of 5 cheaper, but they're not stocked at distributors yet. (Example part at Mouser.)

author: BravoV
author_rank: Super Contributor
timestamp: October 28, 2019, 05:19:08 am
content: Quote from: exmadscientist on October 28, 2019, 05:16:51 amYeah, you're right, those I pointed out is for 100V rated.

author: MagicSmoker
author_rank: Super Contributor
timestamp: October 28, 2019, 09:45:15 am
content: Since the OP's question has been answered, note that there are C0G caps rated for up to 330n and 100V that only cost $5.78 on Mouser:https://www.mouser.com/ProductDetail/KEMET/C2220C334J1GACTU?qs=sGAEpiMZZMs7ZEmUmaUL0%252BHfn%252BkysyX5xyIpm1WOce8%3D

author: ZaphodBeeblebrox
author_rank: Contributor
timestamp: October 29, 2019, 05:38:34 pm
content: Quote from: blueskull on October 28, 2019, 04:10:10 amThere is this thing about leakage current you might want to consider...

author: fabiodl
author_rank: Frequent Contributor
timestamp: October 30, 2019, 12:57:47 am
content: It is "funny" that in their schematic/bom they use x7r and not c0g even for the low pass output filter

author: floobydust
author_rank: Super Contributor
timestamp: October 30, 2019, 05:52:12 am
content: It's better C0G as they have lower dielectric absoption, critical in say a reconstruction filter, but not as much here because the DAC's output impedance and 470R resistor work around it.Signal distortion from high-K ceramic capacitorsMaxim AN4333only looks at X7R, Y5V and the low freq. <300Hz gets badly distorted.The eval boards are usually to play with developing S/W and few have test results showing it actually achieves 24-bit resolution with low noise. +3.3VA also powers the DAC IC'sVD digital portion which might not be ideal.