A simple CMOS digital controlled oscillator with high resolution and linearity

This paper presents a new DCO (digital controlled oscillator) circuit which has a very simple structure with high resolution and linearity. For example, a six bit DCO only requires seventeen MOS transistors. As a result of the simple structure, the new DCO also consumes less power compared to other DCO designs. Another added feature of this new design is that the output signal can be phase-locked to an external input signal. A four bit DCO test circuit was fabricated with a 0.7 /spl mu/m CMOS technology. The test circuit has a die size of 0.024 mm/sup 2/ and an operating frequency range from 13 MHz to 50 MHz.