A digitally-tuned oscillator (DTO) includes a digital-to-analog converter (DAC) and an RC oscillator. The RC oscillator includes an RC circuit for forming a time constant equal to the RC product. However, this RC time constant is not used in the manner of a typical RC network to set the frequency of...http://www.google.se/patents/US5552748?utm_source=gb-gplus-sharePatent US5552748 - Digitally-tuned oscillator including a self-calibrating RC oscillator circuit
