Multiphase clock generator
Aspects of the subject disclosure may include, for example, a multiphase clock generator having a plurality of digital phase interpolators each configured to create a generated clock signal according to an applied digital code, wherein a first digital code applied to a first digital phase interpolator and a second digital code applied to a second digital phase interpolator are chosen in a less precise range such that a first generated clock signal output by the first digital phase interpolator is as close to an ideal phase separation from a second generated clock signal output by the second digital phase interpolator, and wherein additional codes are applied to other digital phase interpolators in a more precise range to create generated clock signals having a deviation from an ideal separation from the first generated clock signal or the second generated clock signal that is less than a linear resolution of the applied digital code. Other embodiments are disclosed.
1 . A multiphase clock generator, comprising:
a plurality of digital phase interpolators each configured to create a generated clock signal according to an applied digital code,
wherein a first digital code applied to a first digital phase interpolator of the plurality of digital phase interpolators and a second digital code applied to a second digital phase interpolator of the plurality of digital phase interpolators are chosen in a less precise range such that a first generated clock signal provided by the first digital phase interpolator deviates within an acceptable range from an ideal phase separation from a second generated clock signal provided by the second digital phase interpolator, and
wherein additional codes are applied to other digital phase interpolators of the plurality of digital phase interpolators in a more precise range to create generated clock signals having a deviation from an ideal separation from the first generated clock signal or the second generated clock signal that is less than a linear resolution of the applied digital code.
2 . The multiphase clock generator of claim 1 , wherein each digital phase interpolator of the plurality of digital phase interpolators comprises:
a first input clock port;
a second input clock port;
an output clock port; and
a plurality of tri-state gates having thermometer weighting code ports,
wherein the applied digital code is used to create thermometer weights provided to the thermometer weighting code ports to control the plurality of tri-state gates to create the generated clock signal,
wherein the generated clock signal is interpolated between a first clock signal applied to the first input clock port and a second clock signal applied to the second input clock port, and
wherein the generated clock signal is provided to the output clock port.
3 . The multiphase clock generator of claim 2 , wherein each digital phase interpolator of the plurality of digital phase interpolators further comprises: a binary to thermometer decoder that converts the applied digital code into the thermometer weights provided to the thermometer weighting code ports.
4 . The multiphase clock generator of claim 3 , further comprising a deskew stage comprising a plurality of deskew units, wherein each deskew unit is coupled to the output clock port of a respective digital phase interpolator of the plurality of digital phase interpolators, wherein each deskew unit comprises a second plurality of tri-state gates configured to delay an output clock signal from the respective digital phase interpolator according to a deskew code.
5 . The multiphase clock generator of claim 4 , wherein the second plurality of tri-state gates in each deskew unit has an identical circuit of the plurality of tri-state gates in each digital phase interpolator of the plurality of digital phase interpolators, and wherein the output clock port is coupled to both input clock ports of each deskew unit.
6 . The multiphase clock generator of claim 4 , wherein each digital phase interpolator of the plurality of digital phase interpolators and respective deskew unit comprises: a latch that stores the applied digital code and the deskew code, thereby enabling serialization of the applied digital code and the deskew code.
7 . The multiphase clock generator of claim 4 , further comprising a binary to one-hot decoder circuit configured to select each digital phase interpolator of the plurality of digital phase interpolators and a respective deskew unit when loading the applied digital code and the deskew code.
8 . The multiphase clock generator of claim 4 , wherein the generated clock signals from the plurality of digital phase interpolators are biased toward ranges where the deskew code provides finer deskew than provided by a number of bits in the deskew code due to a non-linearity in each deskew unit.
9 . The multiphase clock generator of claim 1 , wherein the first generated clock signal and the second generated clock signal are separated by ninety degrees, wherein the plurality of digital phase interpolators comprises a bank of four digital phase interpolators, wherein the ideal separation is 22.5 degrees, and wherein the acceptable range is less than two degrees.
10 . The multiphase clock generator of claim 1 , wherein the plurality of digital phase interpolators comprises four banks of four digital phase interpolators, and wherein the multiphase clock generator outputs sixteen different generated clock signals.
11 . A multiphase clock generator, comprising:
a plurality of digital phase interpolators each configured to create a generated clock signal according to an applied digital code, wherein each digital phase interpolator of the plurality of digital phase interpolators comprises:
a first input clock port;
a second input clock port;
an output clock port;
a plurality of tri-state gates having thermometer weighting code ports; and
a binary to thermometer decoder that converts the applied digital code into thermometer weights provided to the thermometer weighting code ports to control the plurality of tri-state gates to interpolate between a first clock signal applied to the first input clock port and a second clock signal applied to the second input clock port to create the generated clock signal,
wherein the generated clock signal is provided to the output clock port.
12 . The multiphase clock generator of claim 11 , wherein a first digital code applied to a first digital phase interpolator of the plurality of digital phase interpolators and a second digital code applied to a second digital phase interpolator of the plurality of digital phase interpolators are chosen in a less precise range such that a first generated clock signal provided by the first digital phase interpolator is as close to an ideal phase separation from a second generated clock signal provided by the second digital phase interpolator, and
wherein additional codes are applied to other digital phase interpolators of the plurality of digital phase interpolators in a more precise range to generate clock signals having a deviation from an ideal separation from the first generated clock signal or the second generated clock signal that is less than a linear resolution of the applied digital code.
13 . The multiphase clock generator of claim 11 , further comprising a deskew stage comprising a plurality of deskew units, wherein each deskew unit is coupled to the output clock port of a respective digital phase interpolator of the plurality of digital phase interpolators, wherein each deskew unit comprises a second plurality of tri-state gates configured to delay an output clock signal from the respective digital phase interpolator according to a deskew code.
14 . The multiphase clock generator of claim 13 , wherein the second plurality of tri-state gates in each deskew unit has an identical circuit of the plurality of tri-state gates in each digital phase interpolator of the plurality of digital phase interpolators, and wherein the output clock port is coupled to both input clock ports of each deskew unit.
15 . The multiphase clock generator of claim 13 , wherein each digital phase interpolator of the plurality of digital phase interpolators and respective deskew unit comprises: a latch that stores the applied digital code and the deskew code, thereby enabling serialization of the applied digital code and the deskew code.
16 . The multiphase clock generator of claim 13 , further comprising a binary to one-hot decoder circuit configured to select each digital phase interpolator of the plurality of digital phase interpolators and respective deskew unit when loading the applied digital code and the deskew code.
17 . The multiphase clock generator of claim 16 , wherein the generated clock signal provided by each digital phase interpolator is biased toward ranges where the deskew code provides finer deskew than provided by a number of bits in the deskew code due to a non-linearity in the respective deskew unit.
18 . The multiphase clock generator of claim 11 , wherein the first clock signal and the second clock signal are separated by ninety degrees and wherein the plurality of digital phase interpolators comprises a bank of four digital phase interpolators.
19 . The multiphase clock generator of claim 11 , wherein the plurality of digital phase interpolators comprises four banks of four digital phase interpolators, and wherein the multiphase clock generator outputs sixteen different generated clock signals.
20 . A method, comprising:
selecting, by a processing system including a processor, a first digital code and a second digital code in a less precise range of clock signals generated by each digital phase interpolator of a plurality of digital phase interpolators, wherein the first digital code and the second digital code are selected such that the clock signals generated by each digital phase interpolator have a phase separation as close as possible to an ideal phase separation;
applying, by the processing system, the first digital code to a first digital phase interpolator of the plurality of digital phase interpolators, which creates a first generated clock signal;
applying, by the processing system, the second digital code to a second digital phase interpolator of the plurality of digital phase interpolators, which creates a second generated clock signal;
selecting, by the processing system, additional codes for other digital phase interpolators of the plurality of digital phase interpolators in a more precise range to generate the clock signals, thereby reducing a deviation from an ideal separation from the first generated clock signal or the second generated clock signal, wherein the deviation is less than a linear resolution of the additional codes; and
applying, by the processing system, the additional codes to the other digital phase interpolators.