Sampling network and clocking scheme for a switched-capacitor integrator

• US 9,558,845 B2
• Filed: 04/30/2015
• Issued: 01/31/2017
• Est. Priority Date: 03/25/2015
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Huang, Wenchang, Sivakumar, Ramkumar
• Primary Examiner(s): HOUSTON, ADAM D
• Application Number:
  US14/700,696
• Publication Number:
  US 20160284420A1
• Time in Patent Office: 642 Days
• Field of Search: 327/337, 327/554
• US Class Current: 1/1
• CPC Class Codes: G11C 27/026 associated with an amplifier G11C27/028 takes precedence
• CPC Class Codes: H03H 19/004 Switched capacitor networks
• CPC Class Codes: H03M 3/342 by double sampling, e.g. correlated double sampling

Abstract

Certain aspects of the present disclosure generally relate to a sampling network of a switched-capacitor integrator and a clocking scheme associated therewith, which may be used in an analog-to-digital converter (ADC), for example. The integrator generally includes five sets of switches which allow for a decreased switching frequency (e.g., halved) at an input stage of the integrator compared to conventional double sampling networks. As a result, the input impedance of the integrator may be increased (e.g., doubled), resulting in lower power consumption and reduced strain on driving circuitry.

Claims

1. A switched-capacitor integrator, comprising:

an amplifier having first and second output nodes and first and second input nodes;

a first integration capacitor coupled between the first output node and the first input node of the amplifier;

a second integration capacitor coupled between the second output node and the second input node of the amplifier;

first and second sampling capacitors, each having a first terminal and a second terminal;

a first set of switches configured, during a first sampling phase of the integrator, to connect first and second voltages of a differential signal with the first terminals of the first and second sampling capacitors, respectively;

a second set of switches configured to connect the second terminals of the first and second sampling capacitors with a reference potential during the first sampling phase of the integrator, wherein a switching frequency of the first set of switches is less than a switching frequency of the second set of switches; and

a third set of switches configured, during a first integration phase of the integrator, to connect the second terminals of the first and second sampling capacitors with the first and second input nodes of the amplifier, respectively.

2. The integrator of claim 1, wherein the switching frequency of the first set of switches is half the switching frequency of the second set of switches.

3. The integrator of claim 1, wherein a switching frequency of the third set of switches is half the switching frequency of the second set of switches.

4. The integrator of claim 1, further comprising a fourth set of switches configured, during the first integration phase of the integrator, to connect the first and second voltages of the differential signal with the first terminals of the second and first sampling capacitors, respectively.

5. The integrator of claim 4, wherein a switching frequency of the fourth set of switches is half the switching frequency of the second set of switches.

6. The integrator of claim 4, wherein the third set of switches and the fourth set of switches are open during the first sampling phase.

7. The integrator of claim 4, wherein during a second sampling phase of the integrator:

the fourth set of switches are configured to connect the first and second voltages of the differential signal with the first terminals of the second and first sampling capacitors, respectively; and

the second set of switches are configured to connect the second terminals of the first and second sampling capacitors with the reference potential.

8. The integrator of claim 7, wherein the first set of switches and the third set of switches are open during the second sampling phase.

9. The integrator of claim 7, further comprising a fifth set of switches, wherein during a second integration phase of the integrator:

the first set of switches are configured to connect the first and second voltages of the differential signal with the first terminals of the first and second sampling capacitors, respectively; and

the fifth set of switches are configured to connect the second terminals of the first and second sampling capacitors with the second and first input nodes of the amplifier, respectively.

10. The integrator of claim 9, wherein a switching frequency of the fifth set of switches is half the switching frequency of the second set of switches.

11. The integrator of claim 9, wherein the second set of switches, the third set of switches, and the fourth set of switches are open during the second integration phase.

12. The integrator of claim 9, wherein:

the first set of switches, the third set of switches, and the fifth set of switches are open during the second sampling phase;

the first set of switches, the second set of switches, and the fifth set of switches are open during the first integration phase; and

the third set of switches, the fourth set of switches, and the fifth set of switches are open during the first sampling phase.

13. The integrator of claim 9, wherein the first integration phase follows the first sampling phase, wherein the second sampling phase follows the first integration phase, and wherein the second integration phase follows the second sampling phase.

14. The integrator of claim 1, wherein the second set of switches are open during the first integration phase.

15. The integrator of claim 1, wherein the third set of switches are open during the first sampling phase.

16. A method for processing a differential signal with a switched-capacitor integrator, comprising:

during a first sampling phase of the integrator, sampling first and second voltages of a differential signal via first and second sampling capacitors, each having a first terminal and a second terminal, wherein the sampling comprises;

connecting, via a first set of switches, the first and second voltages of the differential signal with the first terminals of the first and second sampling capacitors, respectively; and

connecting, via a second set of switches, the second terminals of the first and second sampling capacitors with a reference potential, wherein a switching frequency of the first set of switches is less than a switching frequency of the second set of switches; and

during a first integration phase of the integrator, integrating the sampled first and second voltages of the differential signal, via an amplifier having first and second input nodes and first and second output nodes, wherein a first integration capacitor is coupled between the first output node and the first input node of the amplifier, wherein a second integration capacitor is coupled between the second output node and the second input node of the amplifier, and wherein the integrating comprises connecting, via a third set of switches, the second terminals of the first and second sampling capacitors with the first and second input nodes of the amplifier, respectively.

17. The method of claim 16, wherein the switching frequency of the first set of switches is half the switching frequency of the second set of switches.

18. The method of claim 16, wherein a switching frequency of the third set of switches is half the switching frequency of the second set of switches.

19. The method of claim 16, further comprising connecting, during the first integration phase of the integrator via a fourth set of switches, the first and second voltages of the differential signal with the first terminals of the second and first sampling capacitors, respectively.

20. The method of claim 19, wherein a switching frequency of the fourth set of switches is half the switching frequency of the second set of switches.

21. The method of claim 19, further comprising opening the third set of switches and the fourth set of switches during the first sampling phase.

22. The method of claim 19, further comprising, during a second sampling phase of the integrator:

connecting, via the fourth set of switches, the first and second voltages of the differential signal with the first terminals of the second and first sampling capacitors, respectively; and

connecting, via the second set of switches, the second terminals of the first and second sampling capacitors with the reference potential.

23. The method of claim 22, further comprising opening the first set of switches and the third set of switches during the second sampling phase.

24. The method of claim 22, further comprising, during a second integration phase of the integrator:

connecting, via the first set of switches, the first and second voltages of the differential signal with the first terminals of the first and second sampling capacitors, respectively; and

connecting, via a fifth set of switches, the second terminals of the first and second sampling capacitors with the second and first input nodes of the amplifier, respectively.

25. The method of claim 24, wherein a switching frequency of the fifth set of switches is half the switching frequency of the second set of switches.

26. The method of claim 24, further comprising opening the second set of switches, the third set of switches, and the fourth set of switches during the second integration phase.

27. The method of claim 24, further comprising:

opening the first set of switches, the third set of switches, and the fifth set of switches during the second sampling phase;

opening the first set of switches, the second set of switches, and the fifth set of switches during the first integration phase; and

opening the third set of switches, the fourth set of switches, and the fifth set of switches during the first sampling phase.

28. The method of claim 24, wherein the first integration phase follows the first sampling phase, wherein the second sampling phase follows the first integration phase, and wherein the second integration phase follows the second sampling phase.

29. The method of claim 16, further comprising opening the second set of switches during the first integration phase.

30. The method of claim 16, further comprising opening the third set of switches during the first sampling phase.