Systems and methods for providing a pipelined analog-to-digital converter

1. A system for providing a pipelined Analog-to-Digital Converter, comprising:

a first multiplying Digital-to-Analog Converter (MDAC) stage comprising:

a sub-Analog-to-Digital Converter (ADC) that outputs a value based on an input signal;

a first reference capacitor that is charged to a reference voltage;

a second reference capacitor that is charged to the reference voltage;

a first sampling capacitor that is charged to a sampling voltage;

a second sampling capacitor that is charged to the sampling voltage; and

a plurality of switches that couple the first reference capacitor and the second reference capacitor so that the first reference capacitor and the second reference capacitor are charged during a sampling phase, that couple the first sampling capacitor and the second sampling capacitor so that the first sampling capacitor and the second sampling capacitor are charged during the sampling phase, that couple the first reference capacitor so that the first reference capacitor is parallel to the second sampling capacitor during a hold phase in response to the value output by the sub-ADC having a first value, and that couple the first sampling capacitor so that the first sampling capacitor couples the first reference capacitor and the second sampling capacitor to a reference capacitor of a second MDAC stage during the hold phase in response to the value output by the sub-ADC has the first value.

2. The system of claim 1 , wherein the first MDAC stage further comprises a first current source coupled to the first reference capacitor and a second current source coupled to the second reference capacitor.

3. The system of claim 2 , wherein the first current source and the second current source are cascoded current sources.

4. The system of claim 2 , wherein the first current source charges the first reference capacitor for a given period of time and the second current source charges the second reference capacitor for the given period of time.

5. The system of claim 1 , wherein the first MDAC stage further comprises a zero-crossing detector that controls how long the first sampling capacitor and second sampling capacitor are coupled to an input voltage.

6. The system of claim 5 , wherein the first MDAC stage further comprises a delay circuit that receives an output signal of the zero-crossing detector and provides a delayed signal that controls when the first sampling capacitor and second sampling capacitor are coupled to the input voltage.

7. The system of claim 1 , wherein the sub-ADC is a comparator.

8. The system of claim 1 , wherein the sub-ADC is a flash ADC.

9. The system of claim 1 , wherein the first MDAC stage is a differential MDAC stage.

10. The system of claim 1 , wherein the first reference capacitor and the second reference capacitor are each half the size of the first sampling capacitor and the second sampling capacitor.

11. A method for providing a pipelined Analog-to-Digital Converter, comprising:

in a first multiplying Digital-to-Analog Converter (MDAC) stage:

outputting from a sub-Analog-to-Digital Converter (ADC) a value based on an input signal;

charging a first reference capacitor and a second reference capacitor to a reference voltage;

charging a first sampling capacitor and a second sampling capacitor to a sampling voltage; and

using a plurality of switches to couple the first reference capacitor and the second reference capacitor so that the first reference capacitor and the second reference capacitor are charged during a sampling phase, to couple the first sampling capacitor and the second sampling capacitor so that the first sampling capacitor and the second sampling capacitor are charged during the sampling phase, to couple the first reference capacitor so that the first reference capacitor is parallel to the second sampling capacitor during a hold phase in response to the value output by the sub-ADC having a first value, and to couple the first sampling capacitor so that the first sampling capacitor couples the first reference capacitor and the second sampling capacitor to a reference capacitor of a second MDAC stage during the hold phase in response to the value output by the sub-ADC has the first value.

12. The method of claim 11 , charging the first reference capacitor using a first current source and charging the second reference capacitor using a second current source.

13. The method of claim 12 , wherein the first current source and the second current source are cascoded current sources.

14. The method of claim 12 , wherein the first current source charges the first reference capacitor for a given period of time and the second current source charges the second reference capacitor for the given period of time.

15. The method of claim 11 , wherein controlling how long the first sampling capacitor and second sampling capacitor are coupled to an input voltage using a zero-crossing detector.

16. The method of claim 15 , further comprising providing a delayed signal that controls when the first sampling capacitor and second sampling capacitor are coupled to the input voltage in response to an output of the zero-crossing detector.

17. The method of claim 11 , wherein the sub-ADC is a comparator.

18. The method of claim 11 , wherein the sub-ADC is a flash ADC.

19. The method of claim 11 , wherein the first MDAC stage is a differential MDAC stage.

20. The method of claim 11 , wherein the first reference capacitor and the second reference capacitor are each half the size of the first sampling capacitor and the second sampling capacitor.