A semiconductor integrated circuit operates with a voltage supplied from a first power supply IC to transmit and receive data to and from an external memory. The semiconductor integrated circuit includes: an interface circuit operating with a voltage supplied from a second power supply IC and accessing the external memory to transmit and receive data to and from the external memory; a determination circuit which determines, based on a result of the access by the interface circuit, an AC timing specification between the external memory and the interface circuit to generate control information for controlling an output voltage of the second power supply IC in accordance with the AC timing specification; and a voltage control circuit which controls the output voltage of the second power supply IC in accordance with the control information.