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David Ashman
Associate II
February 20, 2023
Solved

STM32F4 A/D Input Bias Current

I'm not able to find a spec in the STM32F446 datasheet for minimum A/D input bias current. Does anyone know where I can find this info? I need to sample the voltage from a high resistance potentiometer and it would be handy to know if I need to buffer prior to connecting to A/D pin. Thanks!

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waclawek.jan
waclawek.janBest answer
Super User
February 20, 2023

Static current is given by

0693W00000aHChGQAW.png 

But this is never the limiting factor.

This is:

0693W00000aHCopQAG.pngThe ADC input is a switched capacitor,, and you have to ensure it is fully charged to input signal's level during the sampling phase of conversion.

JW

2 replies

waclawek.jan
waclawek.janBest answer
Super User
February 20, 2023

Static current is given by

0693W00000aHChGQAW.png 

But this is never the limiting factor.

This is:

0693W00000aHCopQAG.pngThe ADC input is a switched capacitor,, and you have to ensure it is fully charged to input signal's level during the sampling phase of conversion.

JW

David Ashman
Associate II
March 2, 2023

Thank you @Community member​ This is very helpful.