an apparatus for controlling an i / o interface of a chip operated in multi - power conditions includes an enable signal generator for generating an enable signal based on a chip power down signal ; a reference voltage generator for generating a predetermined reference voltage in response to the enable signal ; a comparator for determining a voltage required for operating the chip by comparing an external power voltage with the reference voltage in response to the enable signal ; and an input / output means for performing an i / o interface function based on the voltage determined according to the comparison result of the comparator .