Patent ID: 8063509

Claim:
A power supply voltage adjusting apparatus comprising: a voltage setting part that, according to a characteristic variation of a semiconductor integrated circuit, sets a first power supply voltage of a first power supply domain module among a plurality of modules in the semiconductor integrated circuit, each module respectively having a different power supply voltage; a detecting part that compares phases of a first clock signal flowing through the first power supply domain module and a second clock signal flowing through a second power supply domain module to detect a phase difference; and a voltage adjusting part that adjusts a second power supply voltage supplied to the second power supply domain module to reduce the phase difference detected by the detecting part, wherein the voltage setting part includes a margin detecting part that detects a difference between a variation dependency and a power supply voltage dependency of delay of the first clock signal as a margin representative of a fluctuation range of the delay of the first clock signal and sets the first power supply voltage of the first power supply domain module to a third power supply voltage obtained by subtracting the margin from the first power supply voltage, the detecting part compares phases of the first clock signal and the second clock signal to detect a phase difference, when the first power supply voltage of the first power supply domain module is set to the third power supply voltage, and the voltage adjusting part adjusts the second power supply voltage supplied to the second power supply domain module to reduce the phase difference detected by the detecting part when the first power supply voltage of the first power supply domain module is set to the third power supply voltage.