STM32F103: HSE Crystal Capacitors

[Michael_CH]

Hello

Which are the correct Capacitors to use for HSE on STM32F103 with the following Crystal?

Frequency: 8 MHz

Load capacitance CL: 20 pF

Thank you in advance for a quick hint.

Regards

Michael

[NAbun.1]

Hello @Peter BENSCH :

What are your thoughts on my most recent post?

I am mainly trying to determine if I need to change the layout of a dense board to change out my 8pF load crystal due to it being a unlikely to work with 10pF of supposed pin capacitance?

Thanks for the help,
Nino

[Peter BENSCH]

@NAbun.1 

We've reached a point where I realise that not only would a new thread have been better for your questions. The TO is talking about STM32F103 and HSE and you are talking about STM32753 and HSE (topic 1) and LSE (topic 2).

But here are a few thoughts:

The topic of accuracy has often been discussed here and is IMHO completely overrated in relation to the load capacitors. The load capacitors are primarily there to create the same environmental conditions for the crystal as were used for its data sheet. Smaller frequency deviations for the LSE can be corrected with Smooth Calibration (see e.g. here). However, there are still frequency variations due to temperature changes and ageing that cannot be (easily) corrected with this method.

If you have very high requirements for frequency stability, you should consider other clock sources, such as a TCXO or GPS synchronised oscillators.

Regards
/Peter