Controlled oscillators have a significant impact on clock distribution in high-frequency microprocessors. This paper describes a novel digitally controlled oscillator (DCO) constructed using adjustable resistors. Its ping-pong architecture significantly reduces the jitter introduced when the control input is updated. The adjustable resistors digitally set the delay of each stage of a current-starved ring oscillator. The oscillator operates from 1.350 GHz to 4.550 GHz in a 180 nm fabrication technology.