Delta-sigma analog-to-digital converter (ADC) having a serialized quantizer output
First Claim
1. An analog-to-digital converter, comprising:
- a noise-shaping filter having an input for receiving an analog signal to be converted to a digital value;
a quantizer having an input coupled to an output of the noise-shaping filter for generating quantized output values at a quantization rate of the quantizer, wherein the quantized output values are from a set of more than two output values;
a digital-to-analog converter having an input for receiving the quantized output values and having an output coupled to an input of the noise-shaping filter for providing a feedback signal, wherein the noise-shaping filter, the quantizer and the digital-to-analog converter form a delta-sigma modulator loop; and
a serial data circuit having an input coupled to an output of the quantizer for generating a serial bit stream representing the quantized output values, wherein a ratio of the bit rate of the serial bit stream to the quantization rate of the quantizer is greater than unity but less than a minimum number of bits required to represent the input of the digital-to-analog converter.
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Abstract
A delta-sigma analog-to-digital converter (ADC) having a serialized quantizer output has a data rate greater than a quantization rate of the delta-sigma modulator, but less than a bit rate determined by the product of the number of bits required to represent the input to a feedback digital-to-analog converter and the quantization rate. Additional information can be encoded in the serial bit stream by selection among redundant codes based on the value of the additional information. The serial bit stream may encode differences between successive quantizer output samples and the additional information may include the absolute value of the quantizer output, synchronization information and/or framing information for distinguishing data corresponding to multiple ADC input channels.
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Citations
29 Claims
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1. An analog-to-digital converter, comprising:
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a noise-shaping filter having an input for receiving an analog signal to be converted to a digital value; a quantizer having an input coupled to an output of the noise-shaping filter for generating quantized output values at a quantization rate of the quantizer, wherein the quantized output values are from a set of more than two output values; a digital-to-analog converter having an input for receiving the quantized output values and having an output coupled to an input of the noise-shaping filter for providing a feedback signal, wherein the noise-shaping filter, the quantizer and the digital-to-analog converter form a delta-sigma modulator loop; and a serial data circuit having an input coupled to an output of the quantizer for generating a serial bit stream representing the quantized output values, wherein a ratio of the bit rate of the serial bit stream to the quantization rate of the quantizer is greater than unity but less than a minimum number of bits required to represent the input of the digital-to-analog converter. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. An analog-to-digital converter, comprising:
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a quantizer for generating a digital output from an analog input signal; and an output encoder for generating a data output of the analog-to-digital converter from the digital output of the quantizer, wherein the data output represents changes in the digital output as a sequence of codes in the data output, and wherein the sequence of codes extends over a set of codes including at least one redundant code, whereby one value of the changes in the digital output is represented by at least two codes, and wherein a pattern of the at least two codes in the data output represents an indication of an absolute level of the digital output.
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15. A decoder circuit for receiving and decoding a serial bit stream representing output values of an analog-to-digital conversion, the decoder circuit comprising:
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a receiver for receiving the serial bit stream, wherein the serial bit stream encodes the output values of the analog-to-digital conversion along with additional information by using redundant codes to express at least one output level of the analog-to-digital conversion; and a decoder for decoding the serial bit stream to obtain the output values, wherein the decoder checks a sequence of codes within the serial bit stream for error by examining a sequence of the redundant codes. - View Dependent Claims (16, 17)
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18. A method of operating an analog-to-digital converter, comprising:
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filtering an input and feedback signals with an analog loop filter; quantizing a result of the filtering to provide quantized output values; providing feedback proportional to a result of the quantizing as an input to the filtering; converting a result of the quantizing to a serial bit stream, wherein a ratio of the bit rate of the serial bit stream to a quantization rate of the quantizing is greater than unity but less than a minimum number of bits required to represent a set of possible values for the feedback provided by the providing. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29)
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Specification