A sigma-delta ADC is described including a passive filter with an input coupled to the ADC input and a filter output. A gain stage has an input connected to the filter output. A quantiser has an input connected to the gain stage output and a quantiser output. The passive filter includes a first filter resistor between the filter input and the filter output and a filter capacitor having first terminal coupled to the filter output. A feedback resistor is coupled between the quantiser output and the filter output and receives a negative of the value of the output to provide negative feedback to the filter output. The gain stage has a capacitor and resistor in series, and a gain element connected to the gain stage input and an output connected to the gain stage output. One terminal of the gain stage capacitor is connected to the gain element output.

A microphone assembly includes a transducer element and a processing circuit. The processing circuit includes an analog-to-digital converter (ADC) configured to receive, sample and quantize a microphone signal generated by the transducer element to generate a corresponding digital microphone signal. The processing circuit includes a feedback path including a digital loop filter configured to receive and filter the digital microphone signal to provide a first digital feedback signal and a digital-to-analog converter (DAC) configured to convert the first digital feedback signal into a corresponding analog feedback signal. The processing circuit additionally includes a summing node at the transducer output configured to combine the microphone signal and the analog feedback signal.

The dynamic range and power efficiency of a voice-activated system may be improved by dynamically adjusting the configuration of the voice-activated system's input path. In one embodiment, a first portion of audio may be received through an input path of the voice-activated system having a first configuration. A characteristic of the first portion of audio may be determined and the input path may be adjusted to a second configuration based on the determined characteristic. A second portion of audio may then be received through the input path having the second configuration, and speech analysis may be performed on the second portion of audio.

An analog-to-digital converter (ADC) is based on single-bit delta-sigma quantization. The ADC includes an integrator, a threshold detector, a feedback block, a range control circuit and an output processing block. The ADC is configured to, based on its own generated digital bitstream, adjust the magnitude of a subtrahend signal in order to achieve autonomous auto-ranging of the ADC during the integration time of a measurement. In particular, the auto-ranging allows for the efficient conversion of an analog input signal with high dynamic range, for example ambient light, to a digital output signal.

Certain aspects of the present disclosure provide amplifiers. Certain aspects of the present disclosure provide methods and apparatus for protecting an such amplifiers, for example an audio amplifier, or a delta-sigma modulator from saturation. One example amplifier generally includes an output stage comprising a plurality of transistors; and a feedback network having an input coupled to an output of the output stage and comprising a plurality of integrators connected in series. At least one of the plurality of integrators generally includes an operational amplifier having an input and an output, a first resistive element coupled to the input of the operational amplifier, a capacitive element coupled between the input and the output of the operational amplifier; and a first switch coupled between the input and the output of the operational amplifier. For certain aspects, the amplifier may be a class-D amplifier or a direct digital feedback amplifier (DDFA).

A voltage-controlled oscillator-based delta-sigma analog-to-digital converter (VCO-based ΔΣ ADC) includes a VCO-based quantizer that includes delay elements to provide VCO outputs based on an analog input signal and combining logic to combine the VCO outputs so as to provide quantized outputs. Detection logic detects saturation of the VCO-based quantizer based on the quantized outputs and at least a portion of the VCO outputs. The VCO-based ΔΣ ADC also includes correction logic to modify the quantized outputs and provide modified quantized outputs in response to the detection logic detecting the saturation of the VCO-based quantizer and to provide the quantized outputs unmodified in the absence of saturation being detected.

A method can include modulating an amplified analog signal into a digital data stream, filtering the digital data stream with a first filter, generating gain control values associated with amplified analog signal based on the filtered data stream with the first filter and filtering the digital data stream with a second filter, and generating output digital values associated with the amplified analog signal based on the filtered data stream with the second filter. Corresponding systems and devices are also disclosed.

In an embodiment, an ADC converter includes a first injection branch and a second injection branch, a first feedback branch and a second feedback branch, an integration node connected to the first and second injection branches and the first and second feedback branches, an integrator connected to the integration node and a comparator connected downstream of the integrator and configured to generate a comparator output signal to control the first and second feedback branches, wherein the first and second injection branches are configured to provide a charge injection dependent on a respective input quantity to the integration node, wherein the input quantity of the first injection branch is selected from a differential voltage signal, a capacitance dependent signal and a current dependent signal, wherein the input quantity of the second injection branch is selected from another one of the differential voltage signal, the capacitance dependent signal and the current dependent signal, and wherein the first and second feedback branches are configured to provide a feedback charge injection dependent on the comparator output signal to the integration node, the first and second feedback branches configured to receive one of a fixed voltage signal or a differential voltage signal.

A method can include modulating an amplified analog signal into a digital data stream, filtering the digital data stream with a first filter, generating gain control values associated with amplified analog signal based on the filtered data stream with the first filter and filtering the digital data stream with a second filter, and generating output digital values associated with the amplified analog signal based on the filtered data stream with the second filter. Corresponding systems and devices are also disclosed.

A microphone assembly includes a transducer element and a processing circuit. The processing circuit includes an analog-to-digital converter (ADC) configured to receive, sample and quantize a microphone signal generated by the transducer element to generate a corresponding digital microphone signal. The processing circuit includes a feedback path including a digital loop filter configured to receive and filter the digital microphone signal to provide a first digital feedback signal and a digital-to-analog converter (DAC) configured to convert the first digital feedback signal into a corresponding analog feedback signal. The processing circuit additionally includes a summing node at the transducer output configured to combine the microphone signal and the analog feedback signal.