Techniques for mute pattern injection for a pulse-density modulation microphone are described. In one or more implementations, a pulse-density modulation (PDM) microphone includes a transducer that receives a pressure wave and produces an analog signal that represents the pressure wave, an analog-to-digital converter (ADC) that receives the analog signal from the transducer and converts the analog signal into a digital PDM signal. The PDM microphone also includes a pattern generator that generates a digital mute signal, a controller that outputs control signals, and a multiplexer that receives the control signals, the digital mute signal, and the digital PDM signal. The multiplexer transmits the digital mute signal or the digital PDM signal, responsive to the control signals.

A class D amplifier receives and amplifies a differential analog signal which is then differentially integrated. Two pulse width modulators generate pulse signals corresponding to the differentially integrated analog signal and two power units generate output pulse signals. The outputs the power units are coupled to input terminals of integrators via a resistor feedback network. An analog output unit converts the pulse signals to an output analog signal. The differential integration circuitry implements a soft transition between mute/un-mute. In mute, the integrator output is fixed. During the soft transition, the PWM outputs change slowly from a fixed 50% duty cycle to a final value to ensure that no pop noise is present in the output as a result of mode change.

Systems and methods are provided for reducing the effects of an impedance mismatch between a communications system and a shared communications medium. A communication system, such as a transceiver within a cable modem, switches between various operating modes including a transmit mode, a receive mode, and a standby mode. The standby mode may be used while the transceiver is in an idle state between modes, such as while changing an amplifier gain states in between transmissions. While transitioning between modes, the impedance presented by the communications system can temporarily fluctuate causing unwanted signal reflections to propagate out of the communications system and on to the shared medium. Circuitry within the communications system, such as transmission circuitry including an adjustable attenuator, may be placed into a hybrid attenuation-isolation mode during the transition causing the magnitude of any unwanted signal reflections to be attenuated and reducing the impact on the shared medium.

A power supply circuit includes an internal power source that receives power supply from an external power source, an abnormality detection circuit that receives power supply from the internal power source to detect abnormalities of the external power source, a protection target circuit that receives the power supply from the external power source, and a protection function unit that restricts electric power supplied to the protection target circuit to a predetermined range, when the abnormality detection circuit detects the abnormalities.

An audio system includes a reference voltage generation circuit to generate a digital encoding signal and generate an analog reference voltage according to the digital encoding signal, wherein, during a booting procedure and/or a shutdown procedure, the analog reference voltage is smoothly increased and/or decreased at a smooth rate related to a bit number of the digital encoding signal; a first analog operational amplifier for receiving the analog reference voltage to generate a common voltage, which is smoothly increased and/or decreased during the booting procedure and/or the shutdown procedure; and a differential analog operational amplifier pair, coupled to the first analog operational amplifier, for receiving a differential audio input signal pair and outputting a differential output voltage pair to drive a load, wherein, during the booting procedure and/or the shutdown procedure, the differential audio output signal pair is smoothly increased and/or decreased.

The present disclosure discloses an audio output circuit including an audio power amplifier, a mute control circuit and a microcontroller, the audio power amplifier includes a power input terminal, a mute control terminal and an audio signal output terminal, the power input terminal is used to connect a power supply to obtain a power supply voltage, the mute control terminal is connected with the microcontroller through the mute control circuit and is grounded by a pull-down resistor, the audio signal output terminal is used to output an audio signal, the mute control circuit is also connected to the power supply for disconnecting the mute control terminal from the microcontroller when the power supply voltage is less than a preset voltage. The present disclosure also provides an audio device. According to the present disclosure, it is possible to effectively prevent the POP sound of the speaker of the audio device.

A class D amplifier receives and amplifies a differential analog signal which is then differentially integrated. Two pulse width modulators generate pulse signals corresponding to the differentially integrated analog signal and two power units generate output pulse signals. The outputs the power units are coupled to input terminals of integrators via a resistor feedback network. An analog output unit converts the pulse signals to an output analog signal. The differential integration circuitry implements a soft transition between mute/un-mute. In mute, the integrator output is fixed. During the soft transition, the PWM outputs change slowly from a fixed 50% duty cycle to a final value to ensure that no pop noise is present in the output as a result of mode change.

An audio device includes: a processor configured to perform signal processing on the sound signal according to a value of a parameter; a display; a plurality of operating elements; a controller configured to: change the value of the parameter in accordance with an operation performed through any one of the plurality of operating elements; cause the display to display the value of the parameter; and write the value of the parameter in the current memory; and a detector. The controller is configured to: execute a first routine, which is uninterruptable by another routine, when the detector detects the malfunction; and cause, in the first routine, the display to display a first message without newly storing the value of the parameter; and mute, in the first routine, the processed signal in accordance with an operation performed through any one of the plurality of operating elements.

This application describes methods and apparatus for selectively clamping a signal path (106) for an analog audio signal to a clamp voltage, e.g. ground. Voltage clamping circuitry (200) is disclosed having a first switching device (201) in series with a second switching device (202) between a node of the signal path and the clamp voltage. The clamping circuitry is configured to be operable in: a first state where the first and second switching devices are both on to electrically connect the signal path to the clamp voltage; and also a second state to electrically disconnect the signal path from the clamp voltage. In the second state one of the first and second switching devices is configured to block conduction when the voltage at said node of the signal path is positive and the other switching device is configured to block conduction when the voltage at said node of the signal path is negative.

Embodiments described herein provide for detecting presence of an object in proximity to a playback device and responsively performing one or more operations. In an example implementation, a playback device detects, via a proximity detector of the playback device, presence of an object in proximity to the playback device. In response to detecting the presence of the object, the playback device performs one or more operations.