A PWM modulator has a quantizer that generates a PWM output signal to speaker driver. When a first voltage swing range is supplied to the speaker driver, the quantizer analog gain is controlled to be a first gain value. When a second PWM drive voltage swing range is supplied to the speaker driver, the analog gain is controlled to be a second gain value. The first and second gain values of the analog gain of the quantizer cause the combined gain of the quantizer and driver to be approximately equal in the two modes. The quantizer has at least two gain-affecting measurable non-ideal characteristics. The quantizer is adjustable using measured first and second values to correct for first and second of the at least two non-ideal characteristics. The gain of the quantizer is calibratable while the quantizer is adjusted using the measured first and second measured values.

Described herein is a modulator with improved metastability in which the control loop remains stable. In one embodiment, the modulator utilizes differently delayed feedback to successive integrators of the control loop to suppress metastability errors without compromising the stability of the control loop. This is accomplished by including one or more quantizers in the control loop. This technique may be applied to control loops of at least second order, i.e., having two or more integrator stages, where at least one feedback term after the first is non-zero.

A sigma-delta analog-to-digital converter including a gain element connected to an integrator. The gain element switches between different gain values during consecutive phases of a clock signal having a different number of clock cycles. A counter is configured to count with a different increment step size dependent on the first and second gain values. The converter may be part of a sensor arrangement with a temperature sensor.

An apparatus in a PWM modulator includes a triangular wave generator that generates a triangular wave and a comparator that is responsive to a signal input to generate a signal output. An output of the PWM modulator is responsive to the comparator signal output. A polarity inversion circuit, coupled between the triangular wave generator and the comparator, is configured in one of the following ways: to provide the triangular wave to the comparator when the triangular wave has a first slope polarity and to provide a polarity-inverted version of the triangular wave to the comparator when the triangular wave has a second slope polarity opposite the first slope polarity; and to provide the signal input to the comparator when the triangular wave has the first slope polarity and to provide a polarity-inverted version of the signal input to the comparator when the triangular wave has the second slope polarity.

An apparatus for dynamic range enhancement (DRE) which receives an input signal and provides a DRE output signal is presented. The apparatus has an error correction circuit to apply an error correction factor to the input signal such that the DRE output signal provided by the apparatus is dependent on the input signal and the error correction factor. The error correction factor is representative of an error generated by the apparatus.

A PWM modulator has a quantizer that generates a PWM output signal to speaker driver. When a first voltage swing range is supplied to the speaker driver, the quantizer analog gain is controlled to be a first gain value. When a second PWM drive voltage swing range is supplied to the speaker driver, the analog gain is controlled to be a second gain value. The first and second gain values of the analog gain of the quantizer cause the combined gain of the quantizer and driver to be approximately equal in the two modes. The quantizer has at least two gain-affecting measurable non-ideal characteristics. The quantizer is adjustable using measured first and second values to correct for first and second of the at least two non-ideal characteristics. The gain of the quantizer is calibratable while the quantizer is adjusted using the measured first and second measured values.

An apparatus in a PWM modulator includes a triangular wave generator that generates a triangular wave and a comparator that is responsive to a signal input to generate a signal output. An output of the PWM modulator is responsive to the comparator signal output. A polarity inversion circuit, coupled between the triangular wave generator and the comparator, is configured in one of the following ways: to provide the triangular wave to the comparator when the triangular wave has a first slope polarity and to provide a polarity-inverted version of the triangular wave to the comparator when the triangular wave has a second slope polarity opposite the first slope polarity; and to provide the signal input to the comparator when the triangular wave has the first slope polarity and to provide a polarity-inverted version of the signal input to the comparator when the triangular wave has the second slope polarity.

Described herein is a modulator with improved metastability in which the control loop remains stable. In one embodiment, the modulator utilizes differently delayed feedback to successive integrators of the control loop to suppress metastability errors without compromising the stability of the control loop. This is accomplished by including one or more quantizers in the control loop. This technique may be applied to control loops of at least second order, i.e., having two or more integrator stages, where at least one feedback term after the first is non-zero.

Embodiments of multi-mode sigma-delta analog-to-digital converter (ADC) circuits and a microphone circuit are disclosed. In an embodiment, a multi-mode sigma-delta ADC circuit includes a pair of operational transconductance amplifiers (OTAs), a filter connected to the pair of OTAs, a quantizer connected to the filter, a differential digital-to-analog converter (DAC) connected to the quantizer, and a controller configured to switch the multi-mode sigma-delta ADC circuit between a single-ended operational mode, a pseudo differential operational mode, and a full differential operational mode to improve common mode rejection (CMR) performance by controlling the pair of OTAs. An output of a microphone and a differential output of the differential DAC are inputted into input terminals of the pair of OTAs.

Embodiments of sigma-delta analog-to-digital converter (ADC) circuits and a microphone circuit are disclosed. In an embodiment, a sigma-delta ADC circuit includes a pair of operational transconductance amplifiers (OTAs), a filter connected to the pair of OTAs, a quantizer connected to the filter, a differential digital-to-analog converter (DAC) connected to the quantizer, and a bias compensation circuit configured to measure a biasing condition of a first OTA of the pair of OTAs and to apply the biasing condition of the first OTA to a second OTA of the pair of OTAs to reduce Total Harmonic Distortion Plus Noise (THD+N) in the sigma-delta ADC circuit. An output of a microphone and a differential output of the differential DAC are inputted into input terminals of the pair of OTAs.