A voltage controlled current source provides controlled current to a current controlled oscillator in a high frequency phase-locked loop clock generator. The voltage controlled current source receives a first control signal and a set of second control signals indicative of a phase difference between the output signal of the clock signal generator and a reference frequency. It uses those control signals to adjust the current-controlled oscillator. A level shifter coupled to the current-controlled oscillator amplifies the oscillator signals to full rail and adjusts the duty cycle at its output to 50% to produce the clock signal generator output signal.