Correction range technique for multi-range A/D converter
First Claim
1. In a multi-stage A/D converter of the type where at least one stage comprises a flash converter producing two residue signals for the following stage;
- that improvement for providing error correction capability by expanding the operating range of said following stage, comprising;
a first flash stage having output means to produce said two residue signals which together represent a least significant bit (LSB) of said first flash stage;
a second flash stage having an input receiving said residue signals;
said second flash stage having a nominal operating range for processing normal error-free input signals;
said second stage comprising a network responsive to said two residue signals and operable to produce corresponding threshold signals for a set of comparators to produce logic signals representing digitally the magnitude of the input signal defined by said two residue signals;
said network comprising means to produce threshold signals outside of said nominal range of said second stage.
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Abstract
An analog-to-digital converter (ADC) having three cascaded A/D stages of the "flash" type. In the first stage, the analog signal is compared with a set of threshold reference voltages so as to develop a set of most-significant bits and to produce two analog residue signals: (1) a normal residue corresponding to the difference between the analog input and the reference voltage next below the analog input, and (2) a second residue corresponding to the difference between the analog input and the reference voltage next above the analog signal level. These two residue signals are amplified and directed to the second A/D stage. The sum of the residue signals equals one LSB of the first A/D stage, so that the two residues supply to the second stage information about the quantization error of the previous stage as well as the quantization step size to be used to define full-scale at the second stage. The second A/D stage develops a set of less-significant bits and two more residue signals for the third A/D stage. The second stage further includes a capacitor network arranged to effectively double the operating range of that stage to accommodate error correction.
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Citations
14 Claims
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1. In a multi-stage A/D converter of the type where at least one stage comprises a flash converter producing two residue signals for the following stage;
- that improvement for providing error correction capability by expanding the operating range of said following stage, comprising;
a first flash stage having output means to produce said two residue signals which together represent a least significant bit (LSB) of said first flash stage; a second flash stage having an input receiving said residue signals; said second flash stage having a nominal operating range for processing normal error-free input signals; said second stage comprising a network responsive to said two residue signals and operable to produce corresponding threshold signals for a set of comparators to produce logic signals representing digitally the magnitude of the input signal defined by said two residue signals; said network comprising means to produce threshold signals outside of said nominal range of said second stage. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
- that improvement for providing error correction capability by expanding the operating range of said following stage, comprising;
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9. A multi-stage A/D converter comprising at least three successive stages;
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each of said stages including a flash converter for producing a digital flash signal responsive to the analog signal input; at least the first and second of said flash stages including means to develop two residue signals responsive to the relative magnitude of the analog signal and the two quantization signal levels above and below the analog signal; said two residue signals together defining one LSB of that stage; and means associated with each of said flash stages for producing respective digital signals to be combined to produce a final composite output signal. - View Dependent Claims (10, 11, 12, 13, 14)
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Specification