HSE AC timings: tr(HSE), tf(HSE),THSE [STM32H743XGH6]

NiM · ‎2025-07-16

Do you know the specified values for tr, tf and THSE?

KDJEM.1 · ‎2025-09-01

Hello @NiM ;

First of all, I apologize for my late reply.

The design is not sensitive to these parameters (tr and tf).

In bypass mode the signal goes through a GPIO input. So for STM32H7 the constrains are the same as for a GPIO input.

You should respect the VIL and VIH threshold provided in table "Table 60. I/O static characteristics"

I hope this answer your request.

Thank you.

Kaouthar

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Andrew Neil · ‎2025-09-01

T_HSE is just the period of the signal; ie, 1/f_{HSE_ext}

A complex system that works is invariably found to have evolved from a simple system that worked.
A complex system designed from scratch never works and cannot be patched up to make it work.

Andrew Neil · ‎2025-09-01

@KDJEM.1 wrote:
The design is not sensitive to these parameters.

So why does the datasheet call them out like this?

I think the datasheet needs an update to either remove them, or to say that they're unimportant.

A complex system that works is invariably found to have evolved from a simple system that worked.
A complex system designed from scratch never works and cannot be patched up to make it work.