Flash ADC with variable LSB
First Claim
1. A differential analog-to-digital data converter (ADC) for receiving a positive input signal and a negative input signal, comprising:
- a plurality of comparators each associated with a resolution bit of the data converter, one of the inputs of each of said comparators interfaced to a first analog input voltage and the other input of each of the comparators interfaced with a respective reference voltage;
a resolution bit reference device for generating a plurality of successively increasing voltages at respective reference nodes from a first voltage to a second voltage, each of said reference nodes connected to a respective one of the other inputs of said comparators to provide the respective reference voltage, and the voltage difference between said reference nodes defining the resolution of the data converter;
wherein for a substantially a zero difference between the positive and negative input signals, the voltage level of said first analog input voltage is disposed at a voltage above the voltage level on one of said reference nodes and below the voltage level on the next higher one of said reference nodes to constitute the zero code for the data converter; and
a resolution varying device to vary the voltages between said respective nodes in a manner such that the zero code does not substantially vary.
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Accused Products
Abstract
A differential analog-to-digital data converter (ADC) is disclosed for receiving a positive input signal and a negative input signal. A distributed resistive device is provided having taps associated therewith. A plurality of comparators each having a signal input and a reference input are provided, the signal input connected to one of the positive and negative input signals and the reference input connected to a tap on said distributed resistive device. A driver drives current through the distributed resistive device with one of the taps of the distributed resistive device disposed at substantially the other of the positive and negative input signals. A current varying device varys the current through the distributed resistive device to vary the voltage between taps.
38 Citations
17 Claims
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1. A differential analog-to-digital data converter (ADC) for receiving a positive input signal and a negative input signal, comprising:
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a plurality of comparators each associated with a resolution bit of the data converter, one of the inputs of each of said comparators interfaced to a first analog input voltage and the other input of each of the comparators interfaced with a respective reference voltage; a resolution bit reference device for generating a plurality of successively increasing voltages at respective reference nodes from a first voltage to a second voltage, each of said reference nodes connected to a respective one of the other inputs of said comparators to provide the respective reference voltage, and the voltage difference between said reference nodes defining the resolution of the data converter; wherein for a substantially a zero difference between the positive and negative input signals, the voltage level of said first analog input voltage is disposed at a voltage above the voltage level on one of said reference nodes and below the voltage level on the next higher one of said reference nodes to constitute the zero code for the data converter; and a resolution varying device to vary the voltages between said respective nodes in a manner such that the zero code does not substantially vary. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A differential analog-to-digital data converter (ADC) for receiving a positive input signal and a negative input signal, comprising:
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a distributed resistive device having taps associated therewith; a plurality of comparators each having a signal input connected to one of the positive and negative input signals and a reference input connected to a tap on said distributed resistive device; a driver for driving current through said distributed resistive device with one of the taps of said distributed resistive device disposed at substantially the other of said positive and negative input signals; and a current varying device for varying the current through said distributed resistive device to vary the voltage between taps and maintain the zero code unvarying. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17)
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Specification