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inverting output of opamp to MCU adc in differntial mode

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israel_Y

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Hello,

can i connect an inverted opamp output (0 to -3.3V output) to ADC of microcontroller (stm32) configured in differential mode. From The MCU datashet it says [In differential input mode, the analog voltage to be converted for channel “i” is the difference between the external voltage ADC_INi (positive input) and ADC_INi+1 (negative input).]

So i would be connecting gnd/Vcm=0 of opamp to ADC_INi and the negative opamp output to ADC_INi+1. will this work.

Thank you in advance for your time and answers.
 

Dear israel_Y,

The easiest way to do it is using another Opamp and inverting it again, I draw it for you in the attached file, check please and tell me if that is helpful for you.

Have a nice day,

Best regards,
Juan
 

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  • TO_ADC.JPG
    TO_ADC.JPG
    9.1 KB · Views: 86

Hi Juan_zo,

Thank you for your answer. but i am avoiding adding any opamp or ADC buffer.. i was looking a way around simply
 

Dear israel_Y,

I was thinking in your question and I thought in a pasive adder, If you connect a resistor to +3V and you signal source give voltage values between -3 to 0V, then, in resistors' midle point, you will have values from 0 to +1.5V.
I hope it cal help you.

Have a nice day,

Best regards,
Juan
 

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  • 0_3V.JPG
    0_3V.JPG
    8.5 KB · Views: 90
Dear juan,

Thank u so much. is the drawing at the positive input of the opamp?? (or could u draw the circuit with the opamp)? have u simulated the circuit?

Thank you
 

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