Mostly-digital open-loop ring oscillator delta-sigma adc and methods for conversion
AssigneeThe Regents of the University of California
InventorsIan Galton, Gerry Taylor
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Abstract
A continuous-time delta-sigma modulator for analog-to-digital conversion includes a pair of pseudo-differential signal paths including a pair of pseudo-differential signal paths including current-controlled ring oscillators as the load of open-loop common-source amplifiers that are driven by an analog input signal. The signal path produces digital values by sampling the open-loop current-controlled ring oscillators. A calibration circuit measures nonlinear distortion coefficients in a replica of the signal path. A nonlinearity corrector corrects digital values based upon the nonlinear distortion coefficients
Claims25
A continuous time delta-sigma modulator for analog to digital conversion, comprising:
- a signal converter comprising a pair of pseudo-differential voltage controlled ring oscillator signal paths, each signal path comprising a pseudo-differential V/I circuit, a pair of current-controlled ring oscillators and a digital processor that processes outputs of the ring oscillators and conducts nonlinearity correction, wherein each pseudo-differential V/I circuit includes a pair of source degenerated open-loop common-source amplifiers with the current-controlled ring oscillators as loads;
- on-chip with the signal processor, a calibration unit having a replica signal path driven by a pseudo-random calibration sequence that continuously measures the nonlinearity of the replica path, calculates new look-up data for the nonlinearity correction, and adaptively adjusts the center frequency of each current-controlled ring oscillator.
A continuous-time delta-sigma modulator for analog-to-digital conversion, comprising:
- a pair of pseudo-differential signal paths including current-controlled ring oscillators as the load of open-loop common-source amplifiers that are driven by an analog input signal, the signal path producing digital values by sampling the current-controlled ring oscillators;
- a calibration circuit that measures nonlinear distortion coefficients in a replica of said signal path;
- and
- a nonlinearity corrector correcting said digital values based upon said nonlinear distortion coefficients.
A continuous time delta-sigma modulator for analog to digital conversion, comprising:
- pseudo-differential signal conversion means for digitally processing an input analog signal;
- open-loop V/I conversion means within said pseudo-differential signal conversion means for sampling an input;
- nonlinearity correction means for correcting signal conversion nonlinearity;
- and
- replica signal calibration means for setting the nonlinearity correction means and for adaptively adjusting the open-loop current oscillator means.
A method for analog-to-digital signal conversion, the method comprising:
- driving an open-loop current oscillator with a current derived from open-loop common-source amplifiers that are driven by an analog input signal, the signal path producing digital values by sampling the current-controlled ring oscillators;
- phase converting a signal determined from an output of the ring oscillator and generating an output signal;
- determining nonlinear distortion introduced by said ring oscillator with a replica path including a replica of said open-loop current oscillator and said phase converter;
- and
- correcting said output signal based upon said nonlinear distortion determined in said step of determining.
Dependencies are inferred from the claim text.