Error in AN2867 regarding oscillator choice?

[CSchw.4]

Hello,

I think I found an error in the AN2867 and just wanted to confirm it, before we hack around in hardware.

We use an H7 with an external LSE. Fate landed us on the ABRACON ABS05-32.768kHz with 12.5pF. According to AN2867 it is suitable for the H7 and many others.

Due to problems with the clock (which are not surprising NOW) I digged deeper into it and the H7 with LSE max drive is only suitable for a maximum critical crystal gain of 2.7, with the Abracon having a gain of 2.90612.

And, in fact, all other oscillator with a gain of >2.7 are only compatible with the F0 and F3.

So, am I on the right track with this being an error in the application note?

Best wishes

Christoph

[Imen.D · Accepted solution]

Hello @CSchw.4​ and welcome to the Community 🙂

Thanks for your post. I confirm the typo.

The crystal ABS05-32.768kHz 12.5pF is compatible with F0 and F3, which will be corrected in future revisions. Additionally, other crystals with similar characteristics and gmcrit = 2.9, such as TFX-04 and ECS-.327-12.5-12-TR, can also be referred to.

I submitted an internal ticket ID 149699 in order to correct such typo.

(PS: ID 149699, is an internal tracking number and is not accessible or usable by customers).

Please mark my answer as best by clicking on the "Select as Best" button if it fully answered your question. This will help other users find this solution more quickly.

Imen