Analog-to-digital converter (ADC) having integrator dither injection and quantizer output compensation
AssigneeCirrus Logic, Inc.
InventorJohn L. Melanson
Life of this patent
Estimating the term…
Abstract
An analog-to-digital converter (ADC) having integrator dither injection and quantizer output compensation reduces the probability of unchanging code sequences that occur when the input signal and feedback signal are equal and thus no quantizer output change occurs. In particular, in modulators that are periodically reset, the dither reduces the probability of a stuck code sequence at startup. The effect of the dither is removed from the output of the ADC, either by subtracting an offset value from the result of filtering the quantizer output, or directly from the quantizer output itself.
Claims22
An analog-to-digital converter, comprising:
- a noise-shaping filter;
- a dither generator for generating dither values, wherein an output of the dither generator is coupled to a stage of the noise-shaping filter;
- a quantizer having an input coupled to an output of the noise-shaping filter;
- and
- a dither compensation circuit having a first input coupled to an output of the quantizer, a second input coupled to an output of the dither generator and an output for providing an output of the analog-to-digital-converter, wherein the dither compensation circuit adjusts values determined in conformity with the output of the quantizer to remove an offset caused by introduction of the dither values to the noise-shaping filter.
A method of preventing repeated sequences of constant value at the quantized output of a delta-sigma modulator from causing error in the output of an analog-to-digital converter, comprising:
- injecting a dither value into a noise-shaping filter of the delta-sigma modulator;
- and
- subtracting an offset from values determined in conformity with the quantized output, whereby error due to injection of the dither value is substantially eliminated.
An analog-to-digital converter, comprising:
- a noise-shaping filter;
- a dither generator for generating dither values, wherein an output of the dither generator is coupled to an input of a stage of the noise-shaping filter;
- a quantizer having an input coupled to an output of the noise-shaping filter;
- and
- an adjusting element for adjusting values generated in conformity with the output of the quantizer to remove an offset caused by introduction of the dither values to the noise-shaping filter.
Dependencies are inferred from the claim text.