crystal/resonator capacitor choice for stm32f407

[armindavatgaran]

Posted on May 29, 2015 at 17:43

Hello

How to choose proper capacitors for a specific crystal(e.g. 8MHz)?

Thanks.

[Tesla DeLorean]

Posted on May 29, 2015 at 18:10

I think you'll find there's an application note with formulas.

[armindavatgaran]

Posted on May 29, 2015 at 19:25

Any difference between smd and through hole one?

[stm32forum]

Posted on May 29, 2015 at 21:22

http://www.st.com/web/en/resource/technical/document/application_note/CD00221665.pdf

[Tesla DeLorean]

Posted on May 29, 2015 at 21:28

You'd want to keep the leads as short as possible. As I recall the

http://www.st.com/web/en/resource/technical/document/application_note/CD00221665.pdf

or a related one does address physical layout.

Your primary concern would be the selection of components with the desired electrical characteristics. If your PCB layout provides a means of giving you accurate trace level characteristics you could surely factor those in, or provide yourself with enough margin in the design.

It's typically the LSE that gives most people headaches, as a lot of the 32.768 KHz crystals are the 9 or 12pF ones, and not the 6-7pF that the STM32 circuit was designed for, and consequently they either don't start, to take a very long time to start.

Would also suggest browsing the BOM's for ST's reference boards.