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STM32L09
Associate III
May 25, 2025 3:56 AM UTC
Solved

the Maximum value for RC filter

STM32L09_0-1748145218682.png

If ADC1 is continous mode, what's the maximum value for R14? I think the higher the R14 the better, but if too high, the ADC1 value may lower than real.

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MasterT
MasterTBest answer
Lead II
May 25, 2025 4:16 AM UTC

Depends on sampling rate, 

https://community.st.com/t5/stm32-mcus-products/where-can-i-find-the-adc-input-impedance-of-stm32h743-in/m-p/794789/highlight/true#M277369

High resistance value creates error, but what more important that error is not linear and can't be easily corrected as gain offset ib software.

For 16-bits adc I'd not use R> 20 Ohm, since linearity deteriorates above LSB

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MasterT
MasterTBest answer
Lead II
May 25, 2025 4:16 AM UTC

Depends on sampling rate, 

https://community.st.com/t5/stm32-mcus-products/where-can-i-find-the-adc-input-impedance-of-stm32h743-in/m-p/794789/highlight/true#M277369

High resistance value creates error, but what more important that error is not linear and can't be easily corrected as gain offset ib software.

For 16-bits adc I'd not use R> 20 Ohm, since linearity deteriorates above LSB

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