Systems and methods for providing a pipelined analog-to-digital converter
Systems comprising: a first MDAC stage comprising: a sub-ADC that outputs a value based on an input signal; at least two reference capacitors that are charged to a Vref; at least two sampling capacitors that are charged to a Vin; and a plurality of switches that couple the at least two reference capacitors so that they are charged during a sampling phase, that couple the at least two sampling capacitors so that they are charged during the sampling phase, that couple at least one of the reference capacitors so that it is parallel to one of the at least two sampling capacitors during a hold phase, and that couple the other of the at least two sampling capacitors so that it couples the at least one of the reference capacitors and the one of the at least two sampling capacitors to a reference capacitor of a second MDAC stage.
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;
at least two reference capacitors that are charged to a reference voltage;
at least two sampling capacitors that are charged to a sampling voltage; and
a plurality of switches that couple the at least two reference capacitors so that they are charged during a sampling phase, that couple the at least two sampling capacitors so that they are charged during the sampling phase, that couple at least one of the reference capacitors so that it is parallel to one of the at least two sampling capacitors during a hold phase, and that couple the other of the at least two sampling capacitors so that it couples the at least one of the reference capacitors and the one of the at least two sampling capacitors to a reference capacitor of a second MDAC stage.
2. The system of claim 1 , wherein the first MDAC stage further comprises a first current source coupled to a first of the at least two reference capacitors and a second current source coupled to a second of the at least two reference capacitors.
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 of the at least two reference capacitors for a given period of time and the second current source charges the second of the at least two reference capacitors 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 at least two sampling capacitors 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 at least two sampling capacitors are coupled to the input voltage.
7. The system of claim 1 , wherein the sub-ADC is as 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 at least two reference capacitors are half the size of the at least two sampling capacitors.
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 at least two reference capacitors to a reference voltage;
charging at least two sampling capacitors to a sampling voltage; and
using a plurality of switches to couple the at least two reference capacitors so that they are charged during a sampling phase, to couple the at least two sampling capacitors so that they are charged during the sampling phase, to couple at least one of the reference capacitors so that it is parallel to one of the at least two sampling capacitors during a hold phase, and to couple the other of the at least two sampling capacitors so that it couples the at least one of the reference capacitors and the one of the at least two sampling capacitors to a reference capacitor of a second MDAC stage.
12. The method of claim 11 , charging a first of the at least two reference capacitors using a first current source and charging a second of the at least two reference capacitors 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 of the at least two reference capacitors for a given period of time and the second current source charges the second of the at least two reference capacitors for the given period of time.
15. The method of claim 11 , wherein controlling how long the at least two sampling capacitors 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 at least two sampling capacitors 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 at least two reference capacitors are half the size of the at least two sampling capacitors.