Methods and systems to provide a plurality of signals having respective different phases
View Patent ↗A system for generating multiple synthesized clocks having an input terminal for receiving a reference signal, a phase locked loop circuit coupled to the input signal terminal, where the phase locked loop circuit is capable of generating a plurality of output signals that are frequency locked to the reference signal and having a plurality of different phases, a phase rotator coupled to the phase locked loop circuit, where the phase rotator generates an even greater plurality of phases.
1. A phase locked loop (PLL) circuit comprising:
a phase detector to generate an error signal that represents a difference between a reference phase and a feedback phase;
a filter to provide a control voltage based on the error signal; and
a voltage controlled oscillator configured to receive the control voltage and to generate a plurality of output signals having respective different output phases;
wherein the voltage controlled oscillator includes a plurality of buffers that are configured to oscillate to generate the plurality of respective output signals;
wherein the plurality of buffers have respective inputs and respective outputs; and
wherein the respective outputs are fed back in-phase to the respective inputs.
2. The PLL circuit of claim 1 , wherein the output signals are frequency locked to the reference signal.
3. The PLL circuit of claim 1 , further comprising:
a feedback coupled between the voltage controlled oscillator and the phase detector to provide a feedback signal having the feedback phase.
4. The PLL circuit of claim 1 , wherein the plurality of buffers are series-connected.
5. The PLL circuit of claim 1 , wherein the different output phases of the output signals are based on delays associated with respective buffers of the plurality of buffers.
6. A method of generating a plurality of output signals from a reference signal comprising:
generating an error signal that represents a difference between a phase of the reference signal and a phase of a feedback signal;
filtering the error signal to provide a control voltage; and
generating the plurality of output signals having respective different output phases using the control voltage;
wherein generating the plurality of output signals includes causing a plurality of buffers to oscillate; and
wherein causing the plurality of buffers to oscillate includes feeding back outputs of the buffers in-phase to respective inputs of the buffers.
7. The method of claim 6 , further comprising:
frequency locking the output signals to the reference signal.
8. The method of claim 6 , further comprising:
dividing a frequency of an output signal of the plurality of output signals by a factor to provide the feedback signal.
9. A system comprising:
a phase locked loop configured to generate a plurality of intermediate signals having respective different intermediate phases; and
a phase rotator configured to rotate among the plurality of intermediate signals to provide an output phase resolution that is greater than an intermediate phase resolution associated with the plurality of intermediate signals.
10. The system of claim 9 , wherein the phase rotator is configured to continuously rotate among the plurality of intermediate signals through 360 degrees.
11. The system of claim 9 , wherein the phase rotator is configured to provide an output signal having a frequency that is shifted with respect to a frequency associated with the plurality of intermediate signals.
12. The system of claim 11 , wherein a difference between the frequency of the output signal and the frequency associated with the plurality of intermediate signals is based on a rotation speed of the phase rotator.
13. A method comprising:
generating a plurality of signals that are frequency locked to a reference signal and that have respective different phases; and
rotating among the plurality of signals to provide an output phase resolution that is greater than a phase resolution associated with the plurality of signals.
14. The method of claim 13 , wherein rotating among the plurality of signals includes continuously rotating among the plurality of signals through 360 degrees.
15. The method of claim 13 , further comprising:
generating an output signal having a frequency that is shifted with respect to a frequency associated with the plurality of signals.
16. The method of claim 15 , wherein a difference between the frequency of the output signal and the frequency associated with the plurality of signals is based on a rotation speed of the phase rotator.