Load Capacitance for RTC and Primary oscillator for STM32G474QET6U

[HDec]

Hi all,

I was looking at STM32G474E-EVAL's schematic and upon inspection of the load capacitance of the RTC and Primary oscillators it seems that the capacitor values chosen were 4.3pF and 1.8pF respectively. However the datasheet for the crystals show a load capacitance value of 6pF and 8pF.

So, I wanted to know how were those capacitor values selected? I'd really appreciate if someone could point me to a resource on how those values are calculated regardless of what the datasheet says.

Thanks!!

[waclawek.jan]

You might want to review AN2867.

JW

[Piranha]

What Jan said or can start with a short simple version:

https://blog.adafruit.com/2012/01/24/choosing-the-right-crystal-and-caps-for-your-design/

And at the end it recommends ST's AN2867 anyway. =)