An HDL model of a digitally controlled oscillator for rapid digital PLL prototyping

Simulating digitally-controlled oscillators (DCOs) presents a challenging trade-off between the accuracy and the speed. Simplistic DCO simulations have been pursued, but had limitations with nonideal effects. Here, an event-driven behavioral model of a DCO which is able to capture arbitrary oscillating frequency tuning curves and to support multiple codeword inputs with varying granularity is presented. The DCO description provides supply voltage and ambient temperature dependencies, as well as the corner tests and random fluctuations for full PVT variability analysis. It is further equipped with thermal and flicker noise models. This fully-featured HDL implementation of a DCO is intended for use in a discrete-event simulation environment along with the synthesizable logic for rapid digital PLL analysis. A usual design case of a clock generator demonstrates the possibility of subtle random noise versus limit cycle optimization in a quick and convenient manner.