Phase-locked loop circuits and methods implementing multiplexer circuit for fine tuning control of digitally controlled oscillators

摘要

Circuits and methods are provided in which fine tuning control of a DCO (digitally controlled oscillator) circuit in a digital PLL circuit is realized by dither controlling a multiplexer circuit under digital control to selectively output one of a plurality of analog control voltages with varied voltage levels that are input to a fractional frequency control port of the DCO to drive tuning elements of the DCO at fractional frequency resolution and achieve continuous fine tuning of the DCO under analog control.