STM32H743XIH6 Crystal Frequency

[chand_p]

Hi ST Support Team,

I am Using STM32H743XIH6 in one of the project.

Having Query related to crystal frequency.

In datasheet frequency characteristics is provided for oscillator input.

In my Design and STM32H743XIH6 Evaluation Board crystal is implemented.

My Design contains 48Mhz Crystal while EVM contains 25Mhz crystal.

Kindly go through the attached schematic capture of developed board waveform capture at PH0-OSC_IN pin.

Getting same waveform as per Evaluation Kit (Find Attached EVM waveform)

Hope waveform we observed will specify the MCU clock requirement in terms of rise time, fall time, VIH & VIL level.

want to make sure that there is no issue in MCU Clock using external 48 Mhz crystal implementation.
in 25 Mhz & 48 Mhz crystal maximum amplitude is going at 1.8V and MCU operating at 3.3V level.
Hoping that the clock at OSC_PIN is satisfying MCU operating level.

Thanks,

[chand_p]

Hi TDK,

As per attached snap STM32 Datasheet suggesting to use Oscillator.

As per above table there is no specific requirement related to Vil, Vih level of crystal / oscillator output clock.

Can we go ahead with 48 Mhz Crystal with previous shared waveform results?

we implemented crystal in our design based on EVM 25 Mhz crystal.
If it must to have use an oscillator than what need to do with PH1-OSCOUT pin of STM32?
As in oscillator mainly providing clock output on single pin.

Kindly confirm which external source need to implement..
Thanks..
 

[TDK]

> Kindly confirm which external source need to implement..

It's up to you. You can use a crystal, or you can use an external clock source.

The 48 MHz crystal you chose will work with the appropriate load caps.

I strongly suspect that the "10 pF" value in the datasheet is misleading. Here is a post by ST to suggest the same:

https://community.st.com/t5/stm32-mcus-products/calculate-external-capacitors-cl1-and-cl2-for-crystal-oscillator/m-p/621261/highlight/true#M230537

Even if it was 10 pF, you should still have load caps of about 6 pF on there. Might want to re-check the math suggested in the guide I linked above.

> If it must to have use an oscillator than what need to do with PH1-OSCOUT pin of STM32?

If you use an external clock source, PH1 doesn't need to be connected to anything.

[chand_p]

Hi TDK,

For clock verification of crystal do we need to follow this snap?

as per above snap there is no data available for VIH & VIL, do we need to consider VIH and VIL level for STM32?
do we consider attached EVM clock capture for our board as reference?

 Thanks..

[chand_p]

Hi TDK,

as per your shared link for clock check on PA8 pin, is there any alternate pin available to check ?

in my BGA package I am not able to check, as there is no net provided on that pin.

Thanks..

[TDK]

VIH and VIL are not relevant for crystal waveform/selection.

MCO is only available on PA8. Outputting a timer PWM signal on any timer channel pin will accomplish nearly the same thing.