Background calibration technique for pipelined A/D converters using simplified histogram-based testing
First Claim
1. A calibration method for a multi-stage analog to digital (A/D) converter, each stage having an analog input, a digital output, an analog residue and a digital residue, a histogram of digital residue codes being used to correct a transfer characteristic of the stage for a given digital output, the method comprising:
- estimating a bound for a current histogram associated with a current digital output code, the estimated bound being used to estimate a discontinuity in the transfer characteristic;
in response to a determination that a current digital residue occurs in the current histogram;
comparing the estimated bound with a gross lock-up detection value and a fine lock-up detection characteristics;
detecting whether a gross lock-up condition exists based on the comparison of the estimated bound with the gross lock-up detection value;
restarting calibration in response to detection of the gross lock-up condition;
in response to detection that there is no gross lock-up condition, detecting whether a fine lock-up condition exists by determining whether the current digital residue satisfies fine lock-up detection characteristics;
in response to detection that there is no fine lock-up condition, modifying the estimated bound based on a comparison of the current digital residue with a fast lock value and a bound window; and
removing the discontinuity in the transfer characteristic of the A/D converter based on the estimated bound.
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Accused Products
Abstract
A method and apparatus are provided for calibrating a multi-stage A/D converter, such as a pipelined A/D converter. The method and apparatus are based on estimating the bounds of histograms of codes from various stages in the A/D converter. Known approaches were effective in calibrating A/D converters but during bound estimation suffered from lock-up conditions from which it could not recover. Embodiments of the present invention describe two mechanisms for recovering from lock-up conditions and a mechanism for fast locking. If neither a gross lock-up condition nor a fine lock-up condition is detected, the estimated bound is modified based on a comparison of a current digital residue with a fast lock value and a bound window. A discontinuity in the transfer characteristic of the A/D converter can then be removed based on the estimated bound.
21 Citations
23 Claims
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1. A calibration method for a multi-stage analog to digital (A/D) converter, each stage having an analog input, a digital output, an analog residue and a digital residue, a histogram of digital residue codes being used to correct a transfer characteristic of the stage for a given digital output, the method comprising:
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estimating a bound for a current histogram associated with a current digital output code, the estimated bound being used to estimate a discontinuity in the transfer characteristic; in response to a determination that a current digital residue occurs in the current histogram; comparing the estimated bound with a gross lock-up detection value and a fine lock-up detection characteristics; detecting whether a gross lock-up condition exists based on the comparison of the estimated bound with the gross lock-up detection value; restarting calibration in response to detection of the gross lock-up condition; in response to detection that there is no gross lock-up condition, detecting whether a fine lock-up condition exists by determining whether the current digital residue satisfies fine lock-up detection characteristics; in response to detection that there is no fine lock-up condition, modifying the estimated bound based on a comparison of the current digital residue with a fast lock value and a bound window; and removing the discontinuity in the transfer characteristic of the A/D converter based on the estimated bound. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A computer-readable medium storing statements and instructions which, when executed, cause a processor to perform a calibration method for a multi-stage analog to digital (A/D) converter, each stage having an analog input, a digital output, an analog residue and a digital residue, a histogram of digital residue codes being used to correct a transfer characteristic of the stage for a given digital output, the method comprising:
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estimating a bound for a current histogram associated with a current digital output code, the estimated bound being used to estimate a discontinuity in the transfer characteristic; in response to a determination that a current digital residue occurs in the current histogram; comparing the estimated bound with a gross lock-up detection value and a fine lock-up detection characteristics; detecting whether a gross lock-up condition exists based on the comparison of the estimated bound with the gross lock-up detection value; restarting calibration in response to detection of the gross lock-up condition; in response to detection that there is no gross lock-up condition, detecting whether a fine lock-up condition exists by determining whether the current digital residue satisfies fine lock-up detection characteristics; in response to detection of that there is no fine lock-up condition, modifying the estimated bound based on a comparison of the current digital residue with a fast lock value and a bound window; and removing the discontinuity in the transfer characteristic of the A/D converter based on the estimated bound. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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Specification