STM32 HSE Crystal

[Avid]

Hello, I'm using an STM32H750VB and am trying to use the HSE crystal to communicate over USB to my computer, but it isn't able to connect to my computer. I suspect that the issue lies with the crystal since I tried to probe it with an oscilloscope and wasn't able to get any sort of reading. Additionally, when I run a timed LED blinking code using the internal oscillator, it works properly, but when using HSE it doesn't blink. I attempted to calculate the values of the capacitors based on the crystal load capacitance of 8pF. Based on the image of the circuit and crystal parameters does it look like there is an issue with compatibility or component values? 

 

 

[jiangfan]

some comments:

0) check and ensure schematics/PCB/component are aligned.

1) it is not good to probe at OSC pins, PH0/PH1, as crystal oscillation may be impacted. It is recommended to probe at MCO pin, PA8, by enabling MCO output from source = HSE after enabling HSE oscillation, for debug purpose enabling MCO output from source = HSI first.

2) if it is confirmed that HSE oscillation is failed (no MCO output from source = HSE), user may tune load caps for crystal, or say changing C16/C17 value to sth. like 8, 10 or 12 pF

[Peter BENSCH]

...I also did the maths: with your high-frequency crystal and R37=330ohms you achieve a gain margin of 0.284 with the STM32H7, which is well below the minimum of 5. Even with R37=0 you only get 1.22.

I'm afraid that you can't use this crystal on the STM32H7 because its ESR at 48MHz would have to be below 25ohms to achieve sufficient gain margin.

Regards
/Peter

[mƎALLEm]

Hello,

A new article "How to select a compatible crystal and load capacitors for STM32 with layout guidelines" has been published today and this thread has been linked to that article in the "Related links" section.

Good reading.