There are standards, but 3.5v isn't one. Big waste of power though to run a 1.2V part at 5.0V, and transistor geometry to make it capable of that. Most FPGA a

There are standards, but 3.5v isn't one. Big waste of power though to run a 1.2V part at 5.0V, and transistor geometry to make it capable of that. Most FPGA and some micros have separate rails for I/O and a low voltage core, like 1.2V.