Claims
- 1. An electronic system comprising:
a digital to analog converter (DAC) having a DAC output; and an analog postfilter having a postfilter input coupled to the DAC output, said analog postfilter including a first direct charge transfer (DCT) coupled filter having a first DCT coupled filter input and a first DCT coupled filter output and a second DCT coupled filter having a second DCT coupled filter input operably connected with the first DCT coupled filter output.
- 2. The electronic system of claim 1, wherein the first direct charge transfer (DCT) coupled filter comprises:
correlated double sampling (CDS) circuitry.
- 3. The electronic system of claim 1, wherein the second DCT coupled filter further comprises:
correlated double sampling (CDS) filter circuitry.
- 4. The electronic system of claim 1, wherein said analog postfilter having a postfilter input coupled to the DAC output further comprises:
a dual common mode switching matrix interposed between the DAC output and the first DCT coupled filter input.
- 5. The electronic system of claim 4, wherein said dual common mode switching matrix interposed between the DAC output and the first DCT coupled filter input further comprises:
a first switch interposed between a node of a DAC sampling capacitor and a DAC common mode reference; a second switch interposed between the node of the DAC sampling capacitor and an operational amplifier input; and a third switch interposed between the operational amplifier input and analog common mode reference.
- 6. The electronic system of claim 5, further comprising:
a correlated double sampling (CDS) capacitor interposed between at least one of said second switch and said third switch and the operational amplifier input.
- 7. The electronic system of claim 5, further comprising:
at a first time, said first switch closed, said second switch open, and said third switch closed.
- 8. The electronic system of claim 5, further comprising:
at a second time, said first switch open, said second switch closed, and said third switch open.
- 9. The electronic system of claim 1, further comprising:
a digital interpolation filter with postfilter droop compensation.
- 10. The electronic system of claim 1, wherein said electronic system comprises at least one of a mobile communications device, a recording device, a computational device, and a sensing device.
- 11. The electronic system of claim 1, further comprising:
a monolithic integrated circuit having said digital to analog converter (DAC) and said analog postfilter.
- 12. A method for use with an electronic system, said method comprising:
coupling a digital to analog converter (DAC) output with an analog post filter having a first direct charge transfer (DCT) coupled filter and a second DCT coupled filter.
- 13. The method of claim 12, wherein said coupling a digital to analog converter (DAC) output with an analog post filter having a first direct charge transfer (DCT) coupled filter and a second DCT coupled filter comprises:
coupling a DAC sampling capacitor to a DAC common mode reference; coupling a first operational amplifier input to an analog common mode reference; and coupling the DAC sampling capacitor to the first operational amplifier input shortly after at least one of decoupling the sampling capacitor from the DAC common mode reference and decoupling the first operational amplifier input from the analog common mode reference.
- 14. The method of claim 13, further comprising:
coupling an output of the first DCT coupled filter with an input of the second DCT coupled filter.
- 15. The method of claim 13, wherein said coupling the DAC sampling capacitor to the first operational amplifier input shortly after at least one of decoupling the sampling capacitor from the DAC common mode reference and decoupling the first operational amplifier input from the analog common mode reference further comprises:
coupling the DAC sampling capacitor to the first operational amplifier input through a correlated double sampling (CDS) capacitor.
- 16. The method of claim 12, further comprising:
coupling the digital to analog converter (DAC) output with the analog post filter in a monolithic integrated circuit.
- 17. The method of claim 12, further comprising:
coupling a DAC input with a postfilter droop compensator.
- 18. A method for use with an electronic system, said method comprising:
filtering a digital to analog converter (DAC) output signal with an analog post filter having a first direct charge transfer (DCT) coupled filter and a second DCT coupled filter.
- 19. The method of claim 18, wherein said filtering a digital to analog converter (DAC) output signal with an analog post filter having a first direct charge transfer (DCT) filter and a second DCT coupled filter comprises:
filtering the DAC output signal with the first DCT coupled filter; and filtering an output of the first DCT coupled filter with the second DCT coupled filter.
- 20. The method of claim 19, wherein said filtering the DAC output signal with the first direct charge transfer (DCT) filter further comprises:
performing correlated double sampling (CDS) on a first operational amplifier error signal.
- 21. The method of claim 19, wherein said filtering an output of the first DCT coupled filter with a second DCT coupled filter further comprises:
performing correlated double sampling (CDS) on a second operational amplifier error signal.
- 22. The method of claim 18, further comprising:
filtering the digital to analog (DAC) output signal with an analog post filter having a first direct charge transfer (DCT) coupled filter and a second DCT coupled filter in a monolithic integrated circuit.
- 23. The method of claim 18, further comprising:
compensating a DAC input signal for postfilter droop.
- 24. An electronic system comprising:
a digital to analog converter (DAC) having a DAC output; and an analog postfilter having a postfilter input coupled to the DAC output, said analog postfilter including at least a dual common mode switching network coupled between the DAC output and a first DCT coupled filter input, and a second DCT coupled filter having a second DCT coupled filter input coupled to a first DCT coupled filter output.
- 25. The electronic system of claim 24, wherein the dual common mode switching network comprises:
a first switch interposed between a node of a sampling capacitor and a DAC common mode reference; a second switch interposed between the node of the sampling capacitor and an operational amplifier input; and a third switch interposed between the operational amplifier input and an analog common mode reference.
- 26. The electronic system of claim 25, further comprising:
a correlated double sampling (CDS) capacitor interposed between at least one of the second switch and the third switch and the operational amplifier input.
- 27. The electronic system of claim 24, further comprising
a single integrated circuit having said digital to analog converter (DAC), the first DCT coupled filter, and said second DCT coupled filter.
- 28. The electronic system of claim 24, wherein the electronic system comprises at least one of a mobile communications device, a recording device, a computational device, and a sensing device.
- 29. A method for use with an electronic system, said method comprising:
coupling a DAC output with a first direct charge transfer (DCT) coupled filter input wherein said coupling a DAC output with a first direct charge transfer (DCT) coupled filter input includes:
coupling a DAC sampling capacitor to a DAC common mode reference with a first switch, coupling the first DCT coupled filter input to an analog common mode reference with a second switch, and the first switch and the second switch controllable such that the DAC sampling capacitor is couplable to the first DCT coupled filter input shortly after at least one of decoupling the DAC sampling capacitor from the DAC common mode reference and decoupling the first DCT coupled filter input from the analog common mode reference; and coupling a first DCT coupled filter output with a second DCT coupled filter input.
- 30. The method of claim 29, further comprising:
manufacturing a monolithic integrated circuit having the DAC output coupled with the first direct charge transfer (DCT) coupled filter input and the first DCT coupled filter output coupled with the second DCT coupled filter input in a single integrated circuit.
- 31. The method of claim 29, further comprising:
coupling a DAC input with a postfilter droop compensator.
- 32. A method for use with an electronic system, said method comprising:
compensating for a difference between a digital common mode reference voltage and an analog common mode reference voltage by coupling a Digital to Analog Converter (DAC) to the digital common mode reference voltage and coupling an analog portion to the analog common mode reference voltage at a first time and coupling at least a portion of the DAC with the analog portion at a second time; filtering a DAC output signal with a first direct charge transfer (DCT) coupled filter; and filtering an output of the DCT coupled filter with a second direct charge transfer (DCT) coupled filter.
- 33. The method of claim 32, further comprising:
filtering the DAC output signal with the first direct charge transfer (DCT) coupled filter and filtering the output of the DCT coupled filter with the second direct charge transfer (DCT) coupled filter in a single integrated circuit.
- 34. The method of claim 32, further comprising:
compensating a DAC input signal for postfilter droop.
- 35. An electronic system comprising:
a digital to analog converter (DAC) having a DAC output; and an analog postfilter having a postfilter input coupled to the DAC output, said analog postfilter including at least a dual common mode switching network coupled between the DAC output and a first DCT coupled filter input.
- 36. The electronic system of 35 further comprising:
a second DCT coupled filter having a second DCT coupled filter input coupled to a first DCT coupled filter output.
RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional Application No. 60/392,363 filed Jun. 27, 2002.
Provisional Applications (1)
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Number |
Date |
Country |
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60392363 |
Jun 2002 |
US |