STM32L1 ADC only clocked by HSI ?

LCE · ‎2025-10-06

Heyho,

just checking the L162 for a new project, then found that the ADC can only be clocked by the HSI.

Is that correct?

If yes, why?

My experience with HSI (and other RC-oscillators) is that it is "mediocre" at best, rather inaccurate and jitters like crazy. Although this might not be a big issue with a 12-bit ADC.

Merci!

STTwo-32 · ‎2025-10-06

Hello @LCE

I confirm that the ADC is clocked only by HSI. For the reason behind this design choice, according to the chapter 12.3.2 of the RM0038:

"To avoid unnecessary consumption while not converting, the ADC digital interface has been designed to operate in a completely independent manner, at its maximum speed using an internal 16 MHz clock source (HSI), whatever the CPU operating frequency (which can range from a few sub-kHz up to 32 MHz)."

Best Regards.

STTwo-32

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STTwo-32 · ‎2025-10-06

Hello @LCE

I confirm that the ADC is clocked only by HSI. For the reason behind this design choice, according to the chapter 12.3.2 of the RM0038:

"To avoid unnecessary consumption while not converting, the ADC digital interface has been designed to operate in a completely independent manner, at its maximum speed using an internal 16 MHz clock source (HSI), whatever the CPU operating frequency (which can range from a few sub-kHz up to 32 MHz)."

Best Regards.

STTwo-32

To give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.

LCE · ‎2025-10-06

Thanks for the info.

Bad idea anyway. ;)

But probably no game stopper for my application.