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I am using a STM32H723ZG board for a project and I must read analog signals so I am using one 16-bit ADC. Based on the datasheet of this microcontroller serie, the maximum ADC clock frequency is 50 MHz for BOOST = 11.

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However when I am configuring the ADC clock frequency with the STM32CubeMX, the ADC clock is automatically set with 96 MHz with no error. I would like to know if this ADC clock frequency configuration (96 MHz) affects negatively to the performance of the ADC (noise or erros in measurements) and if this ADC clock frequency is actually used by the microcontroller or if the microcontroller automatically uses another frequency that does not exceed 50 MHz. enter image description here

I didn't find anything very useful in the documentation related to this question.

devnull
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Carlos T
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    There's usually an optional divider inside the ADC module which takes the clock it's fed from the bus and divided it down to run the ADC internals. – brhans Feb 15 '23 at 12:07
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    My copy of MX (up to date) [says](https://i.imgur.com/x0pK1ff.png) maximum ADC input frequency is 60MHz and complains if I try to set it to 96MHz manually. ST did some stuff with revisions that affected maximum frequencies on the H7 series. Also the clock problem resolution function doesn't try all that hard. You could switch to PLL3 and get exactly 50MHz. – Spehro Pefhany Feb 15 '23 at 14:58

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You must configure the clock to be within the range given in that table. Page 981 in the TRM for that part gives a diagram of the possible clock sources and division stages. The incoming "adc_ker_ck_input" is selected via configuratioin registers in the RCC.

The possible sources for that are in this other table on page 337.

The effects of using the ADC outside the given range are basically unknowable, it may work fine or it may turn your hair green.

edit: I gave you the documents for the H742 initially. They appear to use both the same ADC and RCC setup though. The links are fixed now.

Aaron Linnell
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