Interesting analysis. The gain calculation looks reasonable, but the resistor values marked with the blue question marks can't really be determined from the amplifier stage alone. They depend on the desired gain, input offset, and the characteristics of the shunt resistor used in the overall current-sensing circuit.

Regarding the 3.3 V connection to the non-inverting input, I believe its purpose is to create a reference (offset) rather than simply acting as a pull-up. Since phase current can be positive or negative relative to the shunt reference, biasing the op-amp input around a fixed voltage (often mid-scale or another defined reference) allows the ADC to measure bidirectional current without the output saturating at ground.

It would also be helpful to know which op-amp is being used and what the shunt resistor value is, as those details are needed to calculate the missing resistor values accurately.

 

I think missing resistor values depend on the required gain, offset, op-amp, and shunt value, while the 3.3 V connection likely provides the reference needed to measure bidirectional current without saturating the ADC.

 

I think missing resistor values depend on the required gain, offset, op-amp, and shunt value, while the 3.3 V connection likely provides the reference needed to measure bidirectional current without saturating the ADC.

Hi,

I guess you are new here so welcome to the forum.

In cases where not all the information is directly given, often we just provide ways to do the analysis and hopefully that helps. Mentioning any missing parts is good too though.
Sometimes they don't even label the parts R1, R2, C1, C2, etc., they just draw the diagram with the symbols alone. That makes it hard to refer to individual components.