The IC maxq3180 is a SPI peripheral that takes analog inputs (current, voltage, ...) and does the correct calculation so that an external microcontroller, using the SPI bus, is able to get and maybe display on an LCD those values. The maxq3180 needs a 3.3V power supply so it's better to use a microcontroller with the same supply ... let's say a PIC18F device with SPI port. The power supply for both the PIC and the MAX should be taken from two phases of the 3-phases line under measurement. You can use a small transformer or a small switching regulator ...
But again ... if you do these questions, it seems you have no experience with live circuits so be very very careful because it's dangerous to test and debug such circuits.