Multiplexed sigma-delta A/D converter
First Claim
1. A sigma-delta analog-to-digital converter comprising:
- a plurality N of sigma-delta modulators arranged in parallel having an analog input signal applied thereto and being controlled by a respective modulator clock at a given modulator sampling frequency and providing a respective modulator digital output signal;
signal combining means coupled to said plurality N of sigma-delta modulators for combining the modulator digital output signals from said modulators in phased sequence to form an overall digital output signal, wherein said overall output digital signal has an effective sampling frequency that is a multiple of N times the sampling frequency of the individual modulators; and
filtering means for filtering quantization noise from said overall digital output signal.
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Abstract
A sigma-delta analog-to-digital converter employs multiplexed single-loop modulators in parallel and respectively phased time-divided clocks. The parallel modulators have the effect of producing digital output at a high sampling frequency that is a multiple of the phased switching frequencies applied to the modulator circuits. In one preferred embodiment, four second-order sigma-delta modulators are driven in clocked phased sequence and combined by a multiplexor circuit. Another embodiment employs second-order modulators using RC integrators. A further embodiment replaces the multiplexor with an adder when in-phase modulator clocks are used, and the adder also acts as a simple low pass filter.
54 Citations
20 Claims
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1. A sigma-delta analog-to-digital converter comprising:
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a plurality N of sigma-delta modulators arranged in parallel having an analog input signal applied thereto and being controlled by a respective modulator clock at a given modulator sampling frequency and providing a respective modulator digital output signal; signal combining means coupled to said plurality N of sigma-delta modulators for combining the modulator digital output signals from said modulators in phased sequence to form an overall digital output signal, wherein said overall output digital signal has an effective sampling frequency that is a multiple of N times the sampling frequency of the individual modulators; and filtering means for filtering quantization noise from said overall digital output signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A sigma-delta analog-to-digital converter comprising:
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a plurality N of sigma-delta modulators arranged in parallel having an analog input signal applied thereto and being controlled by a respective modulator clock at a given modulator sampling frequency and providing a respective modulator digital output signal, wherein said sigma-delta modulators are second-order modulators each containing two integrators in sequence and a comparator/latch circuit as an internal A/D converter; signal combining means coupled to said plurality N of sigma-delta modulators for combining the modulator digital output signals from said modulators in phased sequence to form an overall digital output signal, wherein said overall digital output signal has an effective sampling frequency that is a multiple of N times the sampling frequency of the individual modulators; and filtering means for filtering quantization noise from said overall output digital signal. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification