Calibration of digital-to-analog converters
AssigneeAnalog Devices, Inc.
InventorsGil Engel, Paul S. Wilkins
Life of this patent
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Abstract
Techniques that enable calibration of digital-to-analog Converters (DACs) with minimal processing overhead. A single frequency bin can be used to calibrate errors between bits. A low frequency feedback path can be included into a low frequency low power ADC to determine the error signal that exists in the calibration bin. The bits are calibrated when this error signal is minimized. The calibration techniques described provide an extremely efficient and optimal calibration at the DAC output of both static and dynamic errors.
Claims20
A method for measuring non-idealities of a DAC having a plurality of DAC cells and a plurality of redundant DAC cells whose outputs are summed to generate an analog output of the DAC, the method comprising:
- providing digital data to the DAC cells to generate an output spectrum at the analog output of the DAC;
- generating a first digitally-encoded calibration stimulus having a first fundamental energy at a first frequency bin;
- scaling the first digitally-encoded calibration stimulus by a first weighting factor, and providing a first weighted calibration stimulus to a first subset of the redundant DAC cells to generate a first analog tone while the DAC cells generate the output spectrum;
- scaling the first digitally-encoded calibration stimulus by a second weighting factor, and providing a second weighted calibration stimulus to a second subset of the redundant DAC cells to generate a second analog tone while the DAC cells generate the output spectrum, wherein the second weighting factor is selected to cause the first analog tone and the second analog tone to have opposite polarities;
- and
- detecting, in the analog output of the DAC, an error tone at the first frequency bin resulting from the first analog tone and the second analog tone.
A method for measuring non-idealities of a DAC having a plurality of DAC cells and a plurality of redundant DAC cells whose outputs are summed to generate an analog output of the DAC, the method comprising:
- generating a first digitally-encoded calibration stimulus having a first fundamental energy at a first frequency bin;
- scaling the first digitally-encoded calibration stimulus by a first weighting factor to generate a first weighted calibration stimulus;
- providing the first weighted calibration stimulus to the redundant DAC cells to generate a first analog tone;
- providing digital data and an inverted version of the first weighted calibration stimulus to the DAC cells to generate an output spectrum and a second analog tone, while the first weighted calibration stimulus is provided to the redundant DAC cells;
- and
- detecting, in the analog output of the DAC, an error tone resulting from the first analog tone and the second analog tone.
A method for measuring one or both of static errors between DAC cells and timing errors between DAC cells of a multi-gigabit per second DAC having a plurality of DAC cells and a plurality of redundant DAC cells whose outputs are summed to generate an analog output of the DAC, the method comprising:
- providing digital data to the DAC cells to generate an output spectrum at the analog output of the DAC;
- generating a first digitally-encoded calibration stimulus having a first fundamental energy at a first frequency bin;
- scaling the first digitally-encoded calibration stimulus by a first weighting factor, and providing a first weighted calibration stimulus to a first subset of the redundant DAC cells to generate a first analog tone while the DAC cells generate the output spectrum;
- scaling the first digitally-encoded calibration stimulus by a second weighting factor, and providing a second weighted calibration stimulus to a second subset of the redundant DAC cells to generate a second analog tone while the DAC cells generate the output spectrum, wherein the second weighting factor is selected to cause the first analog tone and the second analog tone to have opposite polarities, wherein summing the first analog tone and the second analog tone yields the error tone;
- and
- detecting, in the analog output of the DAC, an error tone at the first frequency bin resulting from the first analog tone and the second analog tone by detecting energy in the analog output of the DAC at the first frequency bin.
Dependencies are inferred from the claim text.