US 4,908,621 AGranted

Autocalibrated multistage A/D converter

AssigneeTektronix, Inc.

InventorsJohn D. Polonio, Bruce J. Penney, John Lewis

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Abstract

An autocalibrated multistage analog to digital converter precisely maintains appropriate error correction levels for each stage during operation of the converter to minimize quantization errors. An error signal is derived from the digital output of the converter based upon the slope of the input analog signal, determined either explicitly via hardware or implicitly via software, and an overflow/underflow condition. The error signal is fed back to a calibration control circuit to generate individual error correction levels for various variable correction devices within the analog to digital converter, such as a variable analog delay device. The variations from nominal established at calibration that are due to age, temperature or other environmental factors generate the error signal that varies from a nominal value and is fed back to alter the various error correction levels to minimize the error variation.

Claims6

Dependent claims

An improved multistage analog to digital converter of the type having a plurality of analog to digital converter stages such that the output of the digital to analog converter stage is subtracted from the analog input to the prior analog to digital converter stage prior to input to the subsequent analog to digital converter stage, the outputs of the analog to digital converter stages being converted to a digital output corresponding to an analog signal input to the first analog to digital converter stage, wherein the improvement comprises:

means for comparing a current output digital signal derived from the analog to digital converter with an immediately preceding output digital signal to produce a slope indicator;
means for generating an out of range indicator from the most significant bits of the digital output of one of the analog to digital converter stages;
means for combining the slope indicator, the out of range indicator and the remaining bits of the digital output of the one analog to digital converter stage to produce an error signal;
and
means for varying error correction levels for each of a plurality of variable correction devices for each analog to digital converter stage in response to the error signal such that the quantization error is minimized during operation of the analog to digital converter.

2 more elements

Dependencies are inferred from the claim text.