Apparatus and methods for digitally compensated multi-bit sigma-delta analog-to-digital conversion
First Claim
1. A digitally compensated multi-bit analog-to-digital converter comprising:
- recycling converter means for repeatedly converting to a digital signal the difference between an input analog signal and a reconstructed prior input analog signal, said reconstructed prior input analog signal comprising a prior input analog signal which has been converted to a digital signal and has been reconverted back to an analog signal to obtain a recycled digital signal;
a digital corrector which is responsive to said recycling converter means, and which digitally corrects said recycled digital signal to obtain a digitally corrected digital signal; and
a digital calibrator which is responsive to said digital corrector, to generate a digitally compensated digital signal and to generate a digital error code, wherein said digital calibrator comprises;
a calibrating circuit which is responsive to said digital corrector, and which obtains a digitally calibrated digital signal; and
a combiner which combines the digitally calibrated digital signal and the digitally corrected digital signal to generate a digitally compensated digital signal; and
a rounder which is responsive to said combiner, and which generates a digital error code.
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Abstract
A digitally compensated multi-bit sigma-delta analog-to-digital converter may be used to achieve high resolution in analog-to-digital conversions using a low oversampling ratio and simplified hardware construction. The digitally compensated multi-bit sigma-delta analog-to-digital converter has a recycling converter which converts an analog signal to a digital signal and which recycles the converted signal at least one time through a sample hold circuit, an analog-to-digital converter and a digital-to-analog converter in order to obtain a 4 bit digital signal. A digital corrector converts the 4 bit digital signal to a 16 bit corrected digital signal. The 16 bit corrected digital signal is used to generate a digitally compensated digital signal and to generate a digital error code. The digitally compensated digital signal is obtained by adding the 16 bit corrected digital signal with a 16 bit calibrated digital signal using an adder. The nine least significant bits of the compensated digital signal, representing a calibration value indicative of the error in the converted digital signal, are obtained using a roundoff circuit and stored in memory. As a result, high resolution in analog-to-digital conversion can be obtained while achieving a low oversampling ratio and simplified hardware construction.
24 Citations
18 Claims
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1. A digitally compensated multi-bit analog-to-digital converter comprising:
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recycling converter means for repeatedly converting to a digital signal the difference between an input analog signal and a reconstructed prior input analog signal, said reconstructed prior input analog signal comprising a prior input analog signal which has been converted to a digital signal and has been reconverted back to an analog signal to obtain a recycled digital signal; a digital corrector which is responsive to said recycling converter means, and which digitally corrects said recycled digital signal to obtain a digitally corrected digital signal; and a digital calibrator which is responsive to said digital corrector, to generate a digitally compensated digital signal and to generate a digital error code, wherein said digital calibrator comprises; a calibrating circuit which is responsive to said digital corrector, and which obtains a digitally calibrated digital signal; and a combiner which combines the digitally calibrated digital signal and the digitally corrected digital signal to generate a digitally compensated digital signal; and
a rounder which is responsive to said combiner, and which generates a digital error code. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A digitally compensated multi-bit sigma-delta analog-to-digital converter comprising:
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a sample-hold circuit which samples the difference between an input signal and a re-constructed analog signal at a first clock, which holds the sampled input signal at a second clock signal and which outputs the sampled difference between the input signal and the re-constructed analog signal; an analog-to-digital converter which receives the output of said sample-hold circuit, and which converts the difference between the input signal and the re-constructed analog signal to a digital signal in response to the second clock signal; a multi-bit digital-to-analog converter which receives the digital signal from the analog-to-digital converter, and which generates the re-constructed analog signal from said digital signal; a digital corrector which is responsive to said analog-to-digital converter, to digitally correct said digital signal; a digital calibrator which supplies a digitally calibrated digital signal corresponding to the digitally corrected digital signal; and an adding means which is responsive to said digital corrector and said digital calibrator, and which adds the digitally corrected digital signal to the digitally calibrated digital signal to generate a digitally compensated digital signal. - View Dependent Claims (10)
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11. A method for converting an analog signal to a digitally compensated multi-bit digital signal comprising the steps of:
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repeatedly converting the difference between an analog input signal and a reconstructed analog signal to a digital signal to obtain a recycled digital signal; digitally correcting said recycled digital signal to obtain a digitally corrected digital signal; and calibrating said digitally corrected digital signal to generate a digitally compensated digital signal and to generate a digital error code, wherein said calibrating step comprises the steps of; obtaining a digitally calibrated digital signal; combining the digitally calibrated digital signal and the digitally corrected digital signal to generate a digitally compensated digital signal; and rounding off the digitally compensated digital signal to generate a digital error code. - View Dependent Claims (12, 13, 14, 15, 16)
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17. A method for converting an analog signal to a digitally compensated multi-bit digital signal comprising the steps of:
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sampling a difference between an input analog signal and a re-constructed analog signal at a first clock signal; holding the sampled difference between the input analog signal and the reconstructed analog signal at a second clock signal; converting the held sampled difference between the input analog signal and the reconstructed analog signal to a digital signal in response to the second clock signal; generating a reconstructed analog signal from said digital signal; digitally correcting said digital signal to obtain a digitally corrected digital signal; supplying a digitally calibrated digital signal corresponding to the digitally corrected digital signal; and adding the digitally corrected digital signal to the digitally calibrated digital signal to generate a digitally compensated digital signal. - View Dependent Claims (18)
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Specification