A digital conversion system including a sigma-delta converter, a tone generator that generates injects a tone signal into the conversion path of the sigma-delta converter at a frequency that is outside operating signal frequency range, a tone detector that isolates and detects a level of the injected tone signal and provides a corresponding tone level value, a tone ratio comparator that converts the tone level value into a tone level ratio and that compares the converted tone level ratio with an expected tone level ratio to provide an error signal, and a loop controller that converts the error signal to a correction signal to adjust a loop filter frequency the sigma-delta converter. Tones may be serially injected one at a time or simultaneously in parallel for determining a measured tone level ratio for comparison with a corresponding one of multiple stored expected tone level ratios.

An apparatus comprises a sigma-delta analog-to-digital converter (ADC) circuit configured to convert an analog input signal to a digital value. The sigma-delta ADC circuit includes a loop filter circuit including at least one loop filter amplifier, a flash ADC circuit including multiple comparators, and a bias control circuit configured to change a biasing of the at least one loop filter amplifier according to outputs of the multiple comparators of the flash ADC circuit.

Exemplary multipath digital microphone described herein can comprise exemplary embodiments of adaptive ADC range multipath digital microphones, which allow low power to be achieved for amplifiers or gain stages, as well as for exemplary adaptive ADCs in exemplary multipath digital microphone arrangements described herein, while still providing a high DR digital microphone systems. Further non-limiting embodiments can comprise an exemplary glitch removal component configured to minimize audible artifacts associated with the change in the gain of the exemplary adaptive ADCs.

An integrated circuit having multiple switched-capacitor delta-sigma data converter circuits includes compensation for voltage reference error due to leakage current that causes reference voltage droop. The reference filter capacitor terminal voltage is maintained by periodic connection to the reference feedback capacitor(s) that are alternately connected to a voltage reference buffer, and the leakage into the reference feedback capacitor networks of disabled converter circuits causes reference voltage droop. The compensation is either determined from the number of converter circuits that are disabled, or from an error between the filter capacitor voltage and a separate voltage reference, and may be applied by adjusting a resistance selectively coupled between the voltage reference buffer output and the filter capacitor, feedback applied to the voltage reference buffer or its input source. Alternatively, or in combination, correction may be applied to the output of the active converters by digital adjustment of output values.

A tracking ADC with adaptive slew rate boosting can dynamically adjust one or more of its operational parameters in response to detecting a slew rate limit condition. In some embodiments, slew rate boosting can include increasing the value of a digital error signal in response to detection of a slew rate limit condition. In other embodiments, slew rate boosting can include increasing a clock frequency of the tracking ADC in response to detection of a slew rate limit condition.

A digital delta-sigma modulator (DDSM) is disclosed with an input signal x[n], an output signal y[n], a quantization error signal e[n] and a dither signal d[n], having an equation described in the z-domain by

Y(z)=STF(z)X(z)+DTF(z)D(z)−NTF(z)E(z)

wherein Y(z), X(z), D(z) and E(z) are z-transforms of the output signal, the input signal, the dither signal, and the quantization error signal, and wherein STF(z), DTF(z) and NTF(z) correspond to a transfer function of the input signal, a transfer function of the dither signal, and a transfer function of the quantization error signal, and wherein the transfer function of the quantization error signal is of the form:

[00001]$\mathrm{NTF}\left(z\right)={\mathrm{Az}}^{-Q}\left(1+\underset{i=1}{\overset{K}{.Math.}}{c}_i{z}^{-i}\right)$

where A, Q and K are constants, coefficients c.sub.i are real valued and c.sub.K≠0 and wherein at least one of the zeroes z.sub.j of

[00002]$\left(1+\underset{i=1}{\overset{K}{.Math.}}{c}_i{z}^{-i}\right)$

satisfies z.sub.j≠+1 for j=1, 2, . . . , K

An integrated circuit having multiple switched-capacitor delta-sigma data converter circuits includes compensation for voltage reference error due to leakage current that causes reference voltage droop. The reference filter capacitor terminal voltage is maintained by periodic connection to the reference feedback capacitor(s) that are alternately connected to a voltage reference buffer, and the leakage into the reference feedback capacitor networks of disabled converter circuits causes reference voltage droop. The compensation is either determined from the number of converter circuits that are disabled, or from an error between the filter capacitor voltage and a separate voltage reference, and may be applied by adjusting a resistance selectively coupled between the voltage reference buffer output and the filter capacitor, feedback applied to the voltage reference buffer or its input source. Alternatively, or in combination, correction may be applied to the output of the active converters by digital adjustment of output values.

Exemplary multipath digital microphone described herein can comprise exemplary embodiments of adaptive ADC range multipath digital microphones, which allow low power to be achieved for amplifiers or gain stages, as well as for exemplary adaptive ADCs in exemplary multipath digital microphone arrangements described herein, while still providing a high DR digital microphone systems. Further non-limiting embodiments can comprise an exemplary glitch removal component configured to minimize audible artifacts associated with the change in the gain of the exemplary adaptive ADCs.

A delta-sigma modulator includes a first amplifier having an input, a feedback control input, and an output. The input is a first input of the delta-sigma modulator. The delta-sigma modulator further includes a first integrator and a first quantizer. The first integrator has an input and an output. The output of the first amplifier is coupled to the input of the first integrator. The first quantizer has an input and an output. The output of the first quantizer is coupled to the feedback control input of the first amplifier.

A delta-sigma modulator includes a first amplifier having an input, a feedback control input, and an output. The input is a first input of the delta-sigma modulator. The delta-sigma modulator further includes a first integrator and a first quantizer. The first integrator has an input and an output. The output of the first amplifier is coupled to the input of the first integrator. The first quantizer has an input and an output. The output of the first quantizer is coupled to the feedback control input of the first amplifier.