The present invention provides a
semiconductor device capable of realizing
power saving and improvement in reliability or reduction in area. A
semiconductor device includes: a power switch connecting an internal power supply in which power is not
shut down and an internal power supply in which power is
shut down; and an internal
voltage determining circuit for determining
voltage of the internal power supply in which power is
shut down.
Voltage of the internal power supply in which power is shut down is generated from
voltage of an external power supply by using a
regulator circuit. When the power of the internal power supply is interrupted, the power switch is turned off, the
regulator circuit is turned off, and an output of the
regulator circuit is shorted to a ground potential. When the power of the internal power supply is resumed, the regulator circuit is turned on, shorting is cancelled, the increased voltage of the internal power supply is determined by the internal voltage determining circuit, operation of a circuit block is started, and the switch is turned on.