Phase interpolator
View Patent ↗Apparatus to implement several high performance phase interpolators are disclosed. Some embodiments are directed to a full-wave integrating phase interpolation core comprising two pairs of in-phase and quadrature-phase current DACs arranged in a cascode architecture to drive an integrating capacitor and produce an interpolation voltage waveform. The current DACs are biased, weighted, and controlled by in-phase and quadrature-phase input clocks to yield an interpolation waveform that presents a phase value between the phases of the input clocks. Some embodiments deploying the interpolator core use feedback circuitry and reference voltages to adjust the common mode and amplitude of the interpolation voltage waveform to obtain both optimal performance and operation within the interpolator linear region or output compliance range. Both the single-core and dual-core implementations, as well as other implementations of the interpolator core, exhibit high power supply rejection, highly linear interpolation, a wide frequency range, and low cost duty cycle correction.
1. A system on a chip device comprising
a clock data recovery circuit device comprising a phase interpolation device, the phase interpolation device comprising:
a positive power supply terminal;
a negative power supply terminal; and
a first interpolation core comprising:
a positive in-phase cascode current source having a positive in-phase input coupled to the positive power supply terminal through a programmable positive in-phase control, and having a positive in-phase output coupled to a first common node;
a positive quadrature phase cascode current source having a positive quadrature phase input coupled to the positive power supply terminal through a programmable positive quadrature phase control, and having a positive quadrature phase output coupled to the first common node;
a negative in-phase cascode current source having a negative in-phase input coupled to the negative power supply terminal through a programmable negative in-phase control, and having a negative in-phase output coupled to the first common node; and
a negative quadrature phase cascode current source having a negative quadrature phase input coupled to the negative power supply terminal through a programmable negative quadrature phase control, and having a negative quadrature phase output coupled to the first common node;
a second interpolation core having a second common node;
a comparator having a plus terminal, a negative terminal, and a phase interpolation output;
wherein the plus terminal of the comparator is coupled to the first common node; and
wherein the negative terminal of the comparator is coupled to the second common node.
2. The device of claim 1 , further comprising a feedback circuit.
3. The device of claim 2 wherein the feedback circuit comprises at least one of, a switched capacitor feedback circuit, and a continuous feedback circuit.
4. The device of claim 3 wherein the cascode current source comprises a first transistor, a second transistor, and a third transistor.
5. The device of claim 4 wherein the first transistor is coupled to a feedback signal.
6. The device of claim 4 wherein the second transistor is coupled to a DAC bias signal.
7. The device of claim 1 further comprising a multiplexor coupled to the first interpolation core and to the second interpolation core, the multiplexor to select one of a plurality of clock inputs.
8. The device of claim 1 further comprising a comparator coupled to the first common node and coupled to the second common node, to generate a clock output.
9. The device of claim 8 , wherein the comparator is configured to operate in a linear range.
10. The device of claim 8 , wherein the comparator is configured to operate as a voltage comparator.
11. The device of claim 1 , further comprising:
a first common mode feedback circuit coupled to the first common node; and
a second common mode feedback circuit coupled to the second common node;
wherein the first common mode feedback circuit comprises a first common mode voltage generator; and
wherein the second common mode feedback circuit comprises a second common mode voltage generator.
12. The device of claim 11 wherein at least one of the first common mode voltage generator and the second common mode voltage generator is coupled to a digital to analog convertor.
13. The device of claim 11 , wherein the first common mode feedback circuit further comprises a first op amp to generate a feedback control signal.
14. The device of claim 11 , further comprising a reference signal wherein the voltage of the reference signal is provided by an output of a digital-to-analog convertor.
15. The device of claim 14 , wherein the digital-to-analog convertor is coupled to at least one EEPROM memory location.
16. The device of claim 14 , wherein the digital-to-analog convertor is coupled to at least one non-EEPROM memory location.
17. A system on a chip integrated circuit semiconductor device comprising:
a positive power supply terminal;
a negative power supply terminal;
a memory core, and
a first interpolation core comprising:
a positive in-phase cascode current source having a positive in-phase input coupled to the positive power supply terminal through a programmable positive in-phase control, and having a positive in-phase output coupled to a first common node;
a positive quadrature phase cascode current source having a positive quadrature phase input coupled to the positive power supply terminal through a programmable positive quadrature phase control, and having a positive quadrature phase output coupled to the first common node;
a negative in-phase cascode current source having a negative in-phase input coupled to the negative power supply terminal through a programmable negative in-phase control, and having a negative in-phase output coupled to the first common node; and
a negative quadrature phase cascode current source having a negative quadrature phase input coupled to the negative power supply terminal through a programmable negative quadrature phase control, and having a negative quadrature phase output coupled to the first common node;
a second interpolation core having a second common node;
a comparator having a plus terminal, a negative terminal, and a phase interpolation output;
wherein the plus terminal of the comparator is coupled to the first common node; and
wherein the negative terminal of the comparator is coupled to the second common node;
wherein the first interpolator core and the second interpolator core configured with a clock data recovery circuit.
18. The semiconductor device of claim 17 , further comprising:
a first common mode feedback circuit coupled to the first common node; and
a second common mode feedback circuit coupled to the second common node;
wherein the first common mode feedback circuit comprises a first common mode voltage generator; and
wherein the second common mode feedback circuit comprises a second common mode voltage generator.