Digitally controlled oscillator with thermometer sigma delta encoded frequency control word

摘要

Systems and methods for generating a thermometer sigma delta encoded frequency control word for controlling a digitally controlled oscillator in accordance with embodiments of the invention are disclosed. In one embodiment, an all digital phase locked loop for generating an output clock signal includes a thermometer pulse coder configured to generate a frequency control word (FCW) that includes thermometer coded signals and a pulse modulated dither signal, and transmit the pulse modulated dither signal over a selected FCW signal line and transmit the thermometer coded signals over other FCW signal lines, and a digitally controlled oscillator to receive a FCW comprising a combined thermometer and pulse modulated signal and generate an output clock signal.

主权项

1. A method for generating an output clock signal from a reference clock signal using an all digital phase locked loop (ADPLL), the method comprising:
generating a frequency control word from a binary encoded frequency control word using a thermometer pulse coder, where the thermometer pulse coder includes a plurality of frequency control word signal lines and the frequency control word includes a plurality of thermometer coded signals and a pulse modulated dither signal; and selecting, using the thermometer pulse coder, one of the plurality of frequency control word signal lines and transmit the pulse modulated dither signal over the selected frequency control word signal line and transmit the thermometer coded signals over a plurality of the other frequency control word signal lines; receiving by a digitally controlled oscillator a frequency control word comprising a combined thermometer and pulse modulated signal via the plurality of frequency control world signal lines and generating an output clock signal at a frequency determined using at least the frequency control word; receiving by a feedback divider the output clock signal from the digitally controlled oscillator and generating a feedback signal; and receiving by a phase detector a reference clock signal and a feedback signal from the feedback divider and generating a phase error signal, which is provided to a digital loop filter configured to generate a binary encoded frequency control word that is input to the thermometer pulse coder.