Phase detectors with extrapolation of timing events
Apparatus and methods for clock synchronization and frequency translation are provided herein. Clock synchronization and frequency translation integrated circuits (ICs) generate one or more output clock signals having a controlled timing relationship with respect to one or more reference signals. The teachings herein provide a number of improvements to clock synchronization and frequency translation ICs, including, but not limited to, reduction of system clock error, reduced variation in clock propagation delay, lower latency monitoring of reference signals, precision timing distribution and recovery, extrapolation of timing events for enhanced phase-locked loop (PLL) update rate, fast PLL locking, improved reference signal phase shift detection, enhanced phase offset detection between reference signals, and/or alignment to phase information lost in decimation.
1. A digital phase-locked loop (DPLL) comprising:
a first timing detector configured to generate a first plurality of digital representations of timing of a first clock signal, wherein the first plurality of digital representations includes a first digital representation of a first timing event and a second digital representation of a second timing event;
a second timing detector configured to generate a second plurality of digital representations of timing of a second clock signal; and
a phase detector configured to provide phase detection based on the first plurality of digital representations and the second plurality of digital representations, wherein the phase detector is configured to generate a first extrapolated timing event based on adjusting the second digital representation by a time interval between the second timing event and the first timing event, wherein the phase detector is configured to provide phase detection based on the first extrapolated timing event, wherein the first timing event corresponds to an edge associated with a carrier frequency of the first clock signal, and the second timing event corresponds to an edge associated with a sub-carrier frequency of the first clock signal.
2. The DPLL of claim 1 , wherein the first clock signal comprises a reference clock signal to the DPLL, and the second clock signal comprises a feedback clock signal to the DPLL.
3. The DPLL of claim 1 , wherein the first clock signal comprises a feedback clock signal to the DPLL, and the second clock signal comprises a reference clock signal to the DPLL.
4. The DPLL of claim 1 , wherein the phase detector is configured to generate the first extrapolated timing event based on backwards extrapolation in time.
5. The DPLL of claim 1 , wherein the phase detector is configured to generate the first extrapolated timing event based on forward extrapolation in time.
6. The DPLL of claim 1 , wherein the first timing detector includes a first time-to-digital converter (TDC) and the second timing detector includes a second TDC.
7. The DPLL of claim 1 , wherein the phase detector is configured to estimate the time interval based on the first plurality of digital representations and the second plurality of digital representations.
8. A digital phase-locked loop (DPLL) comprising:
a first timing detector configured to generate a first plurality of digital representations of timing of a first clock signal, wherein the first plurality of digital representations includes a first digital representation of a first timing event and a second digital representation of a second timing event;
a second timing detector configured to generate a second plurality of digital representations of timing of a second clock signal; and
a phase detector configured to provide phase detection based on the first plurality of digital representations and the second plurality of digital representations, wherein the phase detector is configured to generate a first extrapolated timing event based on adjusting the second digital representation by a time interval between the second timing event and the first timing event, wherein the phase detector is configured to provide phase detection based on the first extrapolated timing event,
wherein the first plurality of digital representations includes a third digital representation of a third timing event, wherein the phase detector is further configured to generate a second extrapolated timing event based on adjusting the digital representation of the third timing event by a time interval between the third timing event and the first timing event.
9. The DPLL of claim 8 , wherein the first clock signal comprises a reference clock signal to the DPLL, and the second clock signal comprises a feedback clock signal to the DPLL.
10. The DPLL of claim 8 , wherein the first clock signal comprises a feedback clock signal to the DPLL, and the second clock signal comprises a reference clock signal to the DPLL.
11. The DPLL of claim 1 , wherein the first timing event conveys phase information of the first clock signal, and the second timing event conveys frequency information of the first clock signal.
12. A method of phase detection in a digital phase-locked loop (DPLL), the method comprising:
generating a digital representation of a first timing event of an input clock signal to a phase detector;
generating a digital representation of a second timing event of the input clock signal;
extrapolating a first extrapolated timing event based on adjusting the digital representation of the second timing event by a time interval between the second timing event and the first timing event; and
providing phase detection using the first extrapolated timing event, wherein the first timing event corresponds to an edge associated with a carrier frequency of the input clock signal, and the second timing event corresponds to an edge associated with a sub-carrier frequency of the input clock signal.
13. The method of claim 12 , wherein the input clock signal comprises a reference clock signal to the DPLL.
14. The method of claim 12 , wherein the input clock signal comprises a feedback clock signal to the DPLL.
15. The method of claim 12 , wherein extrapolating the first extrapolated timing event comprises backwards extrapolation in time.
16. The method of claim 12 , wherein extrapolating the first extrapolated timing event comprises forward extrapolation in time.
17. The method of claim 12 , further comprising using a time-to-digital converter (TDC) to generate the digital representations of the first and second timing events.
18. The method of claim 12 , further comprising estimating the time interval from the input clock signal.
19. The method of claim 12 , further comprising generating a digital representation of a third timing event of the input clock signal, and extrapolating a second extrapolated timing event based on adjusting the digital representation of the third timing event by a time interval between the third timing event and the first timing event.
20. The method of claim 12 , wherein the first timing event conveys phase information of the input clock signal, and the second timing event conveys frequency information of the input clock signal.