An integrated circuit for generating a clock signal includes a voltage conversion unit, a maximum power determination unit, a clock control unit and a clock generator. The voltage conversion unit converts an external power supply voltage into an internal power supply voltage and detects a variance in current consumption of a functional block to generate a detected voltage wherein the functional block consumes a predetermined current using the internal power supply voltage. The maximum power determination unit determines a maximum current consumption of the functional block and converts the maximum current consumption to a corresponding maximum allowed voltage. The clock control unit generates at least one frequency control signal based on a comparison between the detected voltage and the maximum allowed voltage. The clock generator generates the clock signal whose frequency is adjusted according to the frequency control signal.