A monolithic integrated digitally controlled oscillator circuit is discussed. The oscillator has an output frequency range from 19.07 Hz to more than 20 MHz with a resolution of 19.07 Hz. It is fully linear over the complete control range with respect to the digital control word, has the long-term stability of a quartz oscillator, and the output clock edge uncertainty has a standard deviation of less than 0.5 ns. The circuit requires only a reference quartz as an external component. It operates from a single 5-V power supply, is fabricated in a 1.5- mu m double-metal single-poly standard CMOS process, and requires an area of 4.1 mm/sup 2/. >