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TDJ
Senior III
July 6, 2023
Solved

STM32U5 ADC differential input polarity issue - RM0456 error

  • July 6, 2023
  • 1 reply
  • 2362 views

I think RM0456, section 33.4.7 may be wrong describing ADC differential input polarity:
"When channel “i” is configured in differential input mode, its negative input voltage is connected to VINN[i-1]."

According to Figure 218 and my tests the opposite seems to be correct: negative input voltage is connected to VINN[i+1].

RM0456 ADC bug A.png

 

RM0456 ADC bug B.png

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Best answer by Diane POMABIA

Hello @TDJ 

Yes, I confirm this mistake that will be resolved in next revision of Reference Manual.

Regards

Diane

1 reply

ST Employee
July 6, 2023

Hello @TDJ 

Can you give us more details about your feedback. 

Can you confirm if  connection is according to the figure ?

Regards

Diane 

TDJ
TDJAuthor
Senior III
July 6, 2023

@Diane POMABIA I verified that ADC differential input polarity is consistent with Figure 218.
However, the text description at the end of RM0456, section 33.4.7 which reads:
      "When channel “i” is configured in differential input mode, its negative input voltage is connected to VINN[i-1]."
in my opinion is incorrect. Instead of "VINN[i-1]" should be "VINN[i+1]".

That is, if differential positive input is (e.g.) IN3, negative input for this channel is IN4, not IN2.

Diane POMABIABest answer
ST Employee
July 7, 2023

Hello @TDJ 

Yes, I confirm this mistake that will be resolved in next revision of Reference Manual.

Regards

Diane