Pipeline analog-to-digital converter
First Claim
1. An apparatus for producing digital output signals from an analog input signal in a pipelined converter, the apparatus comprising:
- a sample-and-hold amplifier (SHA) circuit that includes an SHA input terminal that is coupled to the analog input signal and an SHA output terminal, wherein the SHA circuit is arranged to provide a sampled voltage (VSHA) that is responsive to the analog input signal;
an evaluator circuit that includes an evaluation input terminal that is coupled to the analog input signal (VIN) and a digital output terminal that is arranged to provide digital codes that are responsive to the analog input signal;
a reference circuit that includes an adjustment input terminal that is coupled to the digital output terminal, and a reference output terminal, wherein the reference circuit is arranged to provide a reference voltage (VREF) that is responsive to at least one of the digital codes; and
a multiplying digital-to-analog converter (MDAC) circuit that includes an MDAC input terminal that is coupled to the SHA output terminal, an MDAC output terminal that is arranged to provide an output voltage (VOUT1), and a reference input terminal (VREFMD) that is arranged receive the reference voltage (VREF), wherein the MDAC circuit is arranged to sample the reference voltage (VREF) and the sampled voltage (VSHA) at substantially the same time.
1 Assignment
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Accused Products
Abstract
DNL and INL errors are minimized in a pipelined converter that is arranged to use reference pre-sampling. An example first stage in the pipelined converter includes a sample/hold amplifier (SHA) circuit, an evaluator circuit, and a multiplying digital-to-analog converter (MDAC) circuit. The evaluator circuit evaluates the input signal in the converter while the SHA circuit samples the input signal. The MDAC samples the SHA output at substantially the same time it samples a reference voltage, where the reference voltage is adjusted in response to the output of the evaluator circuit. Errors due to capacitor mismatching are minimized such that the settling characteristics of the various amplifiers in the circuits dominate the DNL/INL performance.
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Citations
20 Claims
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1. An apparatus for producing digital output signals from an analog input signal in a pipelined converter, the apparatus comprising:
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a sample-and-hold amplifier (SHA) circuit that includes an SHA input terminal that is coupled to the analog input signal and an SHA output terminal, wherein the SHA circuit is arranged to provide a sampled voltage (VSHA) that is responsive to the analog input signal; an evaluator circuit that includes an evaluation input terminal that is coupled to the analog input signal (VIN) and a digital output terminal that is arranged to provide digital codes that are responsive to the analog input signal; a reference circuit that includes an adjustment input terminal that is coupled to the digital output terminal, and a reference output terminal, wherein the reference circuit is arranged to provide a reference voltage (VREF) that is responsive to at least one of the digital codes; and a multiplying digital-to-analog converter (MDAC) circuit that includes an MDAC input terminal that is coupled to the SHA output terminal, an MDAC output terminal that is arranged to provide an output voltage (VOUT1), and a reference input terminal (VREFMD) that is arranged receive the reference voltage (VREF), wherein the MDAC circuit is arranged to sample the reference voltage (VREF) and the sampled voltage (VSHA) at substantially the same time. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. An apparatus for producing digital output signals from an analog input signal in a pipeline converter, the apparatus comprising:
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a sample-and-hold amplifier means that is arranged to provide a sampled voltage (VSHA) that is responsive to the analog input signal (VIN); an evaluator means that is arranged to provide digital codes that are responsive to the analog input signal (VIN); a reference means that is arranged to provide a selected reference voltage (VREF) that is responsive to at least one of the digital codes from the evaluator means; and a multiplying digital-to-analog converter (MDAC) means that is arranged to sample the selected reference voltage (VREF) and the sampled voltage (VSHA) at substantially the same time, and also arranged to provide an output voltage (VOUT1) that is associated with a residue signal of the pipeline converter. - View Dependent Claims (16, 17)
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18. A method for converting an analog input signal to a digital code in the first stage of a pipeline converter, the method comprising:
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sampling the analog input signal during (VIN) a first operating phase with a SHA circuit to provide a sampled signal (VSHA) after the first operating phase; evaluating the analog input signal (VIN) during the first operating phase with an evaluator circuit to provide a digital code after the first operating phase; selecting a reference voltage (VREF) from a reference circuit in response to the digital code before a second operating phase; sampling the sampled signal during the second operating phase with a sampling capacitor (CS) in an MDAC circuit; sampling the selected reference voltage (VREF) during the second operating phase with a feedback capacitor (CF) in the MDAC circuit; and configuring the sampling capacitor, the feedback capacitor, and an amplifier in a feedback loop to adjust an output voltage (VOUT1) during the first operating phase to provide enhanced DNL performance in the pipeline converter. - View Dependent Claims (19, 20)
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Specification