Fully differential reference driver for pipeline analog to digital converter
First Claim
1. An analog to digital signal conversion system comprising:
- an analog to digital converter having a digital signal input line;
a fully differential reference voltage supply coupled to said analog to digital converter by means of a differential signal path, said fully differential reference voltage supply comprising;
a reference resistor adapted to exhibit a reference voltage between first and second nodes thereof in response to a reference current impressed thereupon;
a fully differential amplifier circuit having third and fourth differential signal input nodes, a common mode voltage input node, and fifth and sixth differential signal output nodes, said third and fourth differential signal input nodes coupled to said first and second nodes respectively through respective first and second capacitors, said fifth and sixth differential signal output nodes coupled to said third and fourth differential signal input nodes respectively through respective third and fourth capacitors;
a source of common mode voltage adapted to be switchingly coupled to both said third and fourth differential signal input nodes;
first and second switching devices adapted to switchingly shunt said third and fourth capacitors respectively; and
a third switching device adapted to switchingly couple said first and second nodes.
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Accused Products
Abstract
An analog to digital conversion (ADC) circuit is disclosed including a fully differential reference voltage source. The reference voltage source includes a programmable current supply adapted to drive a programmed current through a resistor so as to establish an initial reference voltage. The initial reference voltage is sampled onto a capacitive network during a first sampling time interval. The capacitive network is coupled to a differential input of a fully differential amplifier, and maintained at a differential output of the differential amplifier during a second output time interval. An output coupling between the differential output and differential input of the differential amplifier acts to maintain stability of the output voltage during the output time interval.
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Citations
33 Claims
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1. An analog to digital signal conversion system comprising:
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an analog to digital converter having a digital signal input line;
a fully differential reference voltage supply coupled to said analog to digital converter by means of a differential signal path, said fully differential reference voltage supply comprising;
a reference resistor adapted to exhibit a reference voltage between first and second nodes thereof in response to a reference current impressed thereupon;
a fully differential amplifier circuit having third and fourth differential signal input nodes, a common mode voltage input node, and fifth and sixth differential signal output nodes, said third and fourth differential signal input nodes coupled to said first and second nodes respectively through respective first and second capacitors, said fifth and sixth differential signal output nodes coupled to said third and fourth differential signal input nodes respectively through respective third and fourth capacitors;
a source of common mode voltage adapted to be switchingly coupled to both said third and fourth differential signal input nodes;
first and second switching devices adapted to switchingly shunt said third and fourth capacitors respectively; and
a third switching device adapted to switchingly couple said first and second nodes. - View Dependent Claims (2)
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3. An audio processing system, comprising:
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an analog audio input device; and
analog to digital converter coupled to said analog to digital converter for converting analog signals to digital signals comprising;
a conversion circuit having an analog signal input, first, second, third, and fourth reference signal inputs, and a digital signal output; and
a reference voltage circuit having a power supply input, a digital voltage setting input, and first, second, third, and fourth reference signal outputs respectively coupled to said first, second, third, and fourth reference signal inputs, said reference voltage circuit including a reference resistor coupled through a sample and hold circuit to fifth and sixth differential inputs of a fully differential amplifier with seventh and eighth differential outputs alternately switchingly coupled to said first, second, third, and fourth reference signal outputs. - View Dependent Claims (4, 5)
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6. A signal processing system, comprising:
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an analog audio input device for providing analog audio signals; and
an analog to digital converter for converting said analog audio signals to digital output signals, said analog to digital converter comprising;
a conversion circuit having an analog signal input, first, second, third, and fourth reference signal inputs, and a digital signal output; and
a reference voltage circuit having a power supply input, a digital voltage setting input, and first, second, third, and fourth reference signal outputs respectively coupled to said first, second, third, and fourth reference signal inputs, said reference voltage circuit including a reference resistor coupled through a sample and hold circuit to fifth and sixth differential inputs of a fully differential amplifier with seventh and eighth differential outputs alternately switchingly coupled to said first, second, third, and fourth reference signal outputs. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13, 14, 15, 17, 18, 19)
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16. An analog to digital converter comprising:
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an input stage having an input and including a sample and hold circuit;
a plurality of analog to digital stages serially coupled with said input stage and with one another; and
a reference voltage circuit adapted to provide a reference voltage to each analog to digital stage of said plurality of analog to digital stages, the reference voltage circuit comprising;
a programmable current supply coupled in series with a resistor and an active load between a source of supply potential and a source of ground potential; and
a differential amplifier having a first differential input and a second differential input, said first differential input coupled through a first capacitor and a switching device to a first terminal of said resistor, said second differential input coupled through a second capacitor and a second switching device to a second terminal of said resistor.
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20. A switched capacitor voltage source comprising:
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a reference voltage supply including a programmable current source coupled in series with a standard resistor, said reference supply having a first terminal output disposed across said resistor;
a sampling circuit including a second terminal input coupled to said first terminal output; and
an amplifier including a third terminal input, a fourth terminal output, and first and second feedback paths coupling said fourth terminal output to said third terminal input, said fourth terminal output adapted to output a first voltage related to a second voltage impressed on said resistor by said programmable current source. - View Dependent Claims (21, 22, 23)
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24. A reference voltage source circuit for an analog to digital converter comprising:
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a programmable current source having a first control input and a current output;
a reference impedance device having first and second ends, said first end coupled to said current output;
a sample and hold circuit having first and second sample and hold inputs coupled to said first and second ends of said reference impedance device respectively, said sample and hold circuit having first and second sample and hold outputs; and
a amplifier circuit having first and second amplifier inputs respectively coupled to said first and second sample and hold outputs, said amplifier circuit having first and second amplifier outputs, said amplifier circuit including a feedback circuit between said amplifier output and amplifier input, wherein said feedback circuit including a first feedback input coupled to said first amplifier output, said feedback circuit including a second control input and a control output, said control output being coupled to said first control input of said programmable current source. - View Dependent Claims (25, 26)
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27. A voltage source adapted for use in an analog to digital converter comprising:
a switched capacitor circuit including a sample and hold portion and an amplifier portion, said sample and hold portion having an input coupled to a programmable current source and an output coupled to an input of said amplifier portion, said sample and hold portion including a switching device for sampling an input voltage and a capacitive device for holding the input voltage. - View Dependent Claims (28, 29, 30)
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31. A sampled voltage source comprising:
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a reference resistor adapted to receive a programmed current to produce a programmed voltage;
a sampling circuit including a storage location and a crowbar switch, an input of said sampling circuit coupled across said reference resistor to sample said programmed voltage; and
an amplifier having an input coupled across an output of said sampling circuit, said amplifier including a feedback circuit coupled between said output of said amplifier and said input of said amplifier.
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32. A sampled voltage source as defined in 31 wherein said storage location comprises a capacitors with a switch.
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33. A sampled voltage source as defined in 32 wherein said amplifier having output impedance substantially lower than an impedance of said reference resistor.
Specification