Dual-cell structure digitally controlled oscillator with portability for clock generation applications

This paper presents a dual-cell structure and cell-based design digitally controlled oscillator (DCO) for high-performance clock generation applications. The proposed dual-cell DCO not only can reduce the intrinsic delay to increase the maximum output frequency significantly but also extend the controllable range. In addition, the proposed digitally controlled delay cell uses the cascading structure to realize the wide output frequency range and high timing resolution at the same time. A DCO chip is fabricated in 0.18 µm CMOS technology, and the core area is 0.003 mm2. Measurement results show that operation range is from 169 MHz to 522 MHz and the finest delay resolution is 2.2 ps. Furthermore, because the proposed DCO is implemented with the digital standard cells, it is a portable design to migrate to different processes easily and reduce design time significantly.