What is the "c17" capacitor for on the Teensy 4.0

Hello,

unfortunately I just removed a capacitor by mistake on my teensy 4.0, it is the "c17" according to the schematic. So far I could not determine what is not working, but probably something will now be fehlerhasft, I suppose. I implement this Teensy in a larger project, for the later troubleshooting (certainly there will alwayswieder errors) it would be good for me to know what this capacitor was there.

Thanks a lot
Greetings Lukas

How about a link to the schematic showing that cap so that we don't have to waste time trying to find it.

Could be worth asking in the forum that supports that board;

yes of course, sorry!

its here, you have to scroll down. The Cap sitz on the Backside close to pin 31

https://www.pjrc.com/store/teensy40.html

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OK, sure. i will ask there, thanks.

It looks like that is cap tied to 3.3V so it is there is keep the rail stable. You probably reduced your immunity to noise a bit.

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thanks for the answer. Does noise in this context mean that the 3.3v may no longer be stable at the output?

There are several other caps on the 3.3V rail of different values. Each value is there to bypass noise of a certain frequency band. The bands do overlap so missing one cap will likely not have a huge effect.

It looks like that cap is close to U3 with is the flash memory chip

But the c17 is on the backside an the U3 on the demand side, or am i wrong?

There are vias through the board. You can be close to a component, even on the other side.

ah ok! I realized yesterday that I must have actually broken something, the AUDIO OUT1B doesn't seem to work anymore (PIN 32). I use the board with 2 audio shields (four Outputs), for this you need the audio out at PIN 32. As digital input PIN 32 still seems to work (I tested this with a button). Too bad, but nciht so bad, fortunately I have another Teensy lying around. :slight_smile:

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