Powering custom target

I am doing power analysis on a custom target. However, there are two devices that I want to connect to the UFO board. One device (A) is the target device that I want to do power analysis on. The other device (B) is a support MCU that communicates with both the CW and the target (A) - sort of a middle man. I do not want the power fluctuation of the support MCU (B) to influence the final target (A) power during the power analysis for accurate analysis.

With this setup would it work to connect the final target device (A) to FILT_HP/LP and connect the support MCU (B) to the VCC3.3V (VTARG_3V3)? Or will the power of the support MCU (B) still affect the power measurements of target (A).

If above is not feasible, how can I ensure B does not affect A? I could power A from a completely separate power supply but how would I avoid a ground loop?

Thanks for any insight!

A vast majority of the voltage you’re measuring comes from the voltage drop across the shunt resistor you’re using on target A. Unless your second target is doing some pretty terrible things to the 3.3V rail, it should have almost no effect on your power traces.