Delta-sigma analog-to-digital converter with error suppression
A delta-sigma analog-to-digital converter (ΔΣ ADC) has a delta-sigma modulator, a decimation filter and an error suppression circuit. The delta-sigma modulator receives an analog input, and converts the analog input into a first digital output. The decimation filter is coupled to the delta-sigma modulator, and generates a second digital output according to the first digital output. The error suppression circuit is coupled to the decimation filter, and receives an error input and injects an error output into the second digital output according to the error input.
1. A delta-sigma analog-to-digital converter, comprising:
a delta-sigma modulator, arranged for receiving an analog input and converting the analog input into a first digital output;
a first decimation filter, coupled to the delta-sigma modulator, the first decimation filter arranged for generating a second digital output according to the first digital output; and
an error suppression circuit, coupled to the first decimation filter, the error suppression circuit arranged for receiving an error input and injecting an error output into the second digital output according to the error input;
wherein the error suppression circuit receives the error input resulting from a digital-to-analog converter (DAC) of the delta-sigma modulator, the error input comprising an inter-symbol interference (ISI) error or an error resulting from clock jitter.
2. The delta-sigma analog-to-digital converter of claim 1 , wherein the first decimation filter includes a plurality of cascaded decimation stages, and the second digital output is an output of a specific decimation stage of the cascaded decimation stages.
3. The delta-sigma analog-to-digital converter of claim 2 , wherein the specific decimation stage is not a last decimation stage of the first decimation filter.
4. The delta-sigma analog-to-digital converter of claim 1 , wherein the error suppression circuit comprises:
an in-band filter, arranged for receiving the error input, and generating a filtered error input according to the error signal;
a second decimation filter, coupled to the in-band filter, the second decimation filter arranged for generating the error output according to the filtered error input; and
an adder, coupled to the first decimation filter and the second decimation filter, the adder arranged for adding the error output to the second digital output.
5. The delta-sigma analog-to-digital converter of claim 4 , wherein the in-band filter has an in-band frequency response with a unity gain.
6. The delta-sigma analog-to-digital converter of claim 1 , wherein the error suppression circuit comprises:
a second decimation filter, arranged for receiving the error input, and generating the error output according to the error input; and
an adder, coupled to the first decimation filter and the second decimation filter, the adder arranged for adding the error output to the second digital output.
7. A delta-sigma analog-to-digital converter, comprising:
a delta-sigma modulator, arranged for receiving an analog input and converting the analog input into a first digital output;
a first signal processing circuit, coupled to the delta-sigma modulator, the first signal processing circuit arranged for adjusting the first digital output to generate a second digital output; and
an error suppression circuit, coupled to the first signal processing circuit, the error suppression circuit arranged for receiving an error input and injecting an error output into the second digital output according to the error input;
wherein the error suppression circuit receives the error input resulting from a digital-to-analog converter (DAC) of the delta-sigma modulator, the error input comprising an inter-symbol interference (ISI) error or an error resulting from clock jitter.
8. The delta-sigma analog-to-digital converter of claim 7 , wherein the first signal processing circuit is a decimation filter.
9. The delta-sigma analog-to-digital converter of claim 8 , wherein the decimation filter includes a plurality of cascaded decimation stages, and the second digital output is an output of a specific decimation stage of the cascaded decimation stages.
10. The delta-sigma analog-to-digital converter of claim 9 , wherein the specific decimation stage is not a last decimation stage of the decimation filter.
11. The delta-sigma analog-to-digital converter of claim 7 , wherein the error suppression circuit comprises:
an in-band filter, arranged for generating a filtered error input according to the error signal;
a second signal processing circuit, coupled to the in-band filter, the second signal processing circuit arranged for adjusting the filtered error input to generate the error output; and
an adder, coupled to the first signal processing circuit and the second signal processing circuit, the adder arranged for adding the error output to the second digital output.
12. The delta-sigma analog-to-digital converter of claim 11 , wherein the in-band filter has an in-band frequency response with a unity gain.
13. The delta-sigma analog-to-digital converter of claim 11 , wherein each of the first signal processing circuit and the second signal processing circuit is a decimation filter.
14. The delta-sigma analog-to-digital converter of claim 7 , wherein the error suppression circuit comprises:
a second signal processing circuit, arranged for adjusting the error input to generate the error output; and
an adder, coupled to the first signal processing circuit and the second signal processing circuit, the adder arranged for adding the error output to the second digital output.
15. The delta-sigma analog-to-digital converter of claim 14 , wherein each of the first signal processing circuit and the second signal processing circuit is a decimation filter.