INA250: Measuring mains current

Thiago,

Thanks for using E2E!

Yes this should be possible, but only on the neutral line. The issue you need to take into account is the common mode of the device. The INA250 can only withstand up to 36Vcm, so you can only perform measurement on the low side here. The device will not survive measurement on the high side. 

Thiago,

check out this forum post concerning the INA302. This device utilizes an external shunt, but is along the lines of the solution you are discussing here. The tricky aspect here with what you propose is that everything internal to our current sense amplifiers is based off of the GND reference, which would be the isolated GND you are looking to create. However, the measurement will be based off of the neutral as a GND reference, so any variation between the isolated GND and the neutral will potentially inject error into the measurement (and cause damage to the device should the Vcm somehow be violated wrt to the GND pin). These might be deal breakers here based on your specs. 

If you are looking for an isolated solution, you might look at the AMC1300 series, which sounds more akin to the schematic you describe above, and some devices in this family also create the floating supply you mention here (although you would need to supply an external shunt for this device). You could also look at the magnetic solutions in our portfolio, such as the TMCS1101.