Algorithmic analog-to-digital converter with reduced differential non-linearity and method
First Claim
Patent Images
1. An analog to digital converter section comprising:
- a converter stage configured to receive an analog input voltage and to produce a converter stage output indicative of the analog input voltage, with the converter stage output including a digital output and a first residue analog voltage output; and
an over-range stage including an amplifier which produces a second residue analog voltage voltage output, and first and second capacitors, with the over-range stage switchable between a sample phase and an amplification phase, with the over-range stage being configured when in the sample phase to connect the first capacitor, and not the first capacitor, to receive the first residue analog voltage when the first residue analog voltage is in a first state and configured to connect the second capacitor, and not the first capacitor, to receive the first residue analog voltage when the first residue voltage is in a second state different from the first state.
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Abstract
An analog to digital converter section for use in an analog to digital converter which includes a converter stage which produces a digital and an residue output. The residue output is applied to an over-range stage which produces a second residue output equal to the first residue output reduced in magnitude by the magnitude of a reference voltage. The over-range stage is capable of operating with a relatively high feedback factor to increase operating speed and with commutated feedback-capacitor switching to reduce differential non-linearity errors.
62 Citations
20 Claims
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1. An analog to digital converter section comprising:
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a converter stage configured to receive an analog input voltage and to produce a converter stage output indicative of the analog input voltage, with the converter stage output including a digital output and a first residue analog voltage output; and an over-range stage including an amplifier which produces a second residue analog voltage voltage output, and first and second capacitors, with the over-range stage switchable between a sample phase and an amplification phase, with the over-range stage being configured when in the sample phase to connect the first capacitor, and not the first capacitor, to receive the first residue analog voltage when the first residue analog voltage is in a first state and configured to connect the second capacitor, and not the first capacitor, to receive the first residue analog voltage when the first residue voltage is in a second state different from the first state. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. An analog to digital converter section comprising:
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a converter stage configured to receive an analog input voltage and to produce a converter stage output indicative of the analog input voltage, with the converter stage output including a digital output and a first residue analog voltage output; and an over-range stage including an amplifier, first and second capacitors and switching circuitry switchable among first, second, third and fourth modes, with the first mode connecting the first capacitor, and not the second capacitor, between an inverting amplifier input and the first residue analog voltage output and connecting an output of the amplifier to the inverting amplifier input, the second mode connecting the first capacitor between the amplifier output and the inverting amplifier input and connecting the second capacitor between the inverting amplifier input and a source of a first reference voltage, the third mode connecting the second capacitor, and not the first capacitor, between the first residue analog voltage output and the inverting amplifier input and connecting an output of the amplifier to the inverting amplifier input, and the fourth mode connecting the first capacitor between the inverting amplifier input and a source of a second reference voltage and connecting the second capacitor between the inverting amplifier input and the amplifier output. - View Dependent Claims (9, 10, 11, 12)
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13. A method of reducing over-range conditions in an algorithmic ADC comprised of a plurality of converter stages, with each of the converter stages alternating between a sample phase and an amplification phase, said method comprising the following steps:
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predicting, prior to an end of the amplification phase of a first one of the converter stages, whether a first residue voltage of the first converter stage will be in a first voltage range or a second voltage range at the end of the amplification phase of the first converter stage; sampling the first residue voltage output of the first converter stage after an end of the amplification phase of the first converter stage to produce a sampled voltage; combining a first reference voltage with the sampled voltage in the event the step of predicting establishes that the first residue voltage is in the first voltage range so as to produce a second residue voltage; combining a second reference voltage, different than the first reference voltage, in the event the step of predicting establishes that the first residue voltage is in the second voltage range so as to produce the second residue voltage; and forwarding the second residue voltage to a second one of the converter stages. - View Dependent Claims (14, 15, 16, 17)
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18. A method of reducing over-range conditions in an algorithmic ADC comprised of a plurality of converter stages, with each of the converter stages alternating between a sample phase and an amplification phase, said method comprising the following steps:
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sampling a first residue voltage produced by the first converter stage on a first capacitor, and not a second capacitor, in the event the first residue voltage is of a first polarity; sampling the first residue voltage on the second capacitor, and not the first capacitor, in the event the first residue voltage is of a second polarity opposite the first polarity; subtracting a first reference voltage from the first residue voltage in the event the first residue voltage was sampled on the first capacitor to produce a second residue voltage; subtracting a second reference voltage from the first residue voltage in the event the first residue voltage was sampled on the second capacitor to produce the second residue voltage; and forwarding the second residue voltage to a subsequent one of the converter stages. - View Dependent Claims (19, 20)
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Specification