Calibration and compensation of delta sigma ADC's and DAC's by correlating noise signals
AssigneeCirrus Logic, Inc.
InventorJohn Laurence Melanson
Life of this patent
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Abstract
The present invention correlates noise from a delta sigma modulator with noise from the same modulator passed through a nonlinear block whose purpose is to isolate the imperfection being measured. Once the imperfection is measured the results may be used to correct the output of the delta sigma modulator, to accept or reject chips or for other purposes.
Claims21
Apparatus for measuring circuit imperfections in an analog to digital converter (ADC) including an analog delta sigma modulator, the apparatus comprising:
- a first decimator connected to the output of the modulator;
- a nonlinear test element connected to the output of the modulator, for applying a nonlinear function to the output of the modulator;
- a second decimator matched to the first decimator and connected to the output of the nonlinear element;
- a correlator connected to the output of the first decimator and the output of the second decimator;
- and
- means for applying a test signal to the ADC;
- wherein the correlator performs a correlation between the output of the first decimator and the output of the second decimator in the presence of the test signal and generates a circuit error signal based upon the correlation.
Apparatus for measuring circuit imperfections in an analog to digital converter (ADC) including at least two analog delta sigma modulators connected to inputs of the ADC, the apparatus comprising:
- a first decimator connected to the output of the first modulator;
- a nonlinear test element connected to the output of the first modulator, for applying a nonlinear function to the output of the first modulator;
- a second decimator matched to the first decimator and connected to the output of the nonlinear element;
- a correlator connected to the output of the first decimator and the output of the second decimator;
- and
- means for applying a test signal to the ADC;
- wherein the correlator performs a correlation between the output of the first decimator and the output of the second decimator in the presence of the test signal and generates a circuit error signal based upon the correlation.
A method of measuring circuit imperfections in a delta sigma analog to digital converter (ADC) including an analog delta sigma modulator, the method comprising the steps of:
- applying a nonlinear function to the output of the modulator;
- performing a correlation between the output of the modulator and the output of the modulator after the nonlinear function is applied;
- and
- generating a circuit error signal based upon the correlation.
Dependencies are inferred from the claim text.