Abstract: A semiconductor integrated circuit includes an internal circuit, a first external power supply connection terminal, a regulator, an external control terminal, transistors, and a second external power supply connection terminal. The internal circuit has first and second operation modes. The internal circuit is driven with different power supply voltages in the first and second modes. An external power supply voltage is supplied to the first external power supply connection terminal when at least the first operation mode is selected. The regulator steps down the external power supply voltage supplied from the first external power supply connection terminal, and supplies the stepped-down voltage to the internal circuit. The external control terminal receives an ON/OFF control signal corresponding to the first or second operation mode. The transistors set the regulator in an enable/disable state based on the ON/OFF control signal supplied from the external control terminal.