Patent ID: 8587366

Claim:
A semiconductor device comprising: a unit configured to, in a period before power up, compare a voltage obtained by dividing a voltage of a first voltage node at a first division ratio with a voltage obtained by dividing a voltage of a second voltage node at a second division ratio and determine whether to activate an enable signal according to a result of the comparison; a voltage driving unit configured to increase the voltage of the second voltage node when the enable signal is activated in the period before power up; and a voltage detection section configured to detect the voltage of the first voltage node in a period after power up and determine whether to activate a second enable signal according to a result of the voltage detection in the period after power up, wherein the voltage driving unit is configured to increase the voltage of the second voltage node when the second enable signal is activated in the period after power up, wherein the voltage driving unit comprises: a signal selection section configured to select one of the enable signal and the second enable signal in response to a power up signal and output an oscillation enable signal in response to the selection; an oscillation signal generation section configured to generate an oscillation signal in an activation period of the oscillation enable signal; and a charge pump configured to perform a charge pumping operation in response to oscillation of the oscillation signal and increase the voltage of the second voltage node.