Cirrus Logic Inc.

Mixsemi Limited

Other

Robin Matthew Tsang

John Christopher Tucker

John L Melanson

Eric J Swanson

Scott Allan Woodford

A data converter is disclosed. The data converter includes a loop-filter, a quantizer, an analog dynamic element matching (DEM) shuffler, a digital DEM shuffler and a feedback digital-to-analog converter. The loop-filter receives analog signals from an analog input. The quantizer then converts the filtered analog signals from the loop-filter to digital signals at a digital output. The analog DEM shuffler shuffles a set of analog threshold levels of the quantizer to yield a set of partially shuffled digital data at an output of the quantizer. The digital DEM shuffler shuffles the set of partially shuffled digital data from the output of the quantizer to yield a set of shuffled digital data. The feedback digital-to-analog converter converts the set of shuffled digital data to a set of analog data to be fed back to the loop-filter.

Delta-sigma modulator having multiple dynamic element matching shufflers

An offset correction circuit removes DC offset from an analog audio output signal by comparing transitions of digital audio values to which the analog output signal is related to the output of a monitor that monitors the analog output signal. The monitor may be a zero-crossing detector and the transitions of the digital signal that are compared may be transitions of the most-significant bit (MSB) of the digital audio values. A filtering algorithm or filter circuit may be used to average a result of the comparison of the transitions, so that the offset is slowly and accurately removed. A chopped or autozero comparator may be used to further reduce error in the offset determination.

Audio amplifier offset reduction using digital input/output comparisons

A modulated gain audio control and zipper noise suppression techniques provide reduction in audible artifacts caused by discrete-valued gain changes. The gain of a signal is controlled by modulating between multiple gain values for corresponding time durations, so that a resulting average gain is controlled according to the average of the multiple gain values as weighted by their corresponding time durations. The modulation frequency is above the bandwidth of the signal. Transitions between gain levels are performed by changing the relative proportion of the durations to slowly change the gain according to a transition profile, which may be linear or non-linear. The modulation employed may be pulse-width modulation, or another modulation pattern such as a delta-sigma modulation pattern.

Modulated gain audio control and zipper noise suppression techniques using modulated gain

A discrete time delta-sigma modulator circuit, which may be used to implement an analog-to-digital converter (ADC) provides improved anti-aliasing performance when lower quantization rates are selected, by maintaining the clocking rate of a first stage in the delta-sigma modulator loop filter at a rate higher than would ordinarily be selected for a lower quantization rate. To accomplish the anti-aliasing improvement, the ratio between the quantization rate and the clocking rate of the first integrator is reduced at the lower quantization rate, resulting in a first true alias image at a multiple of the quantization rate, permitting anti-aliasing filters to more effectively attenuate the alias image, and attenuating the images spaced at the quantization rate via the averaging operation of the first integrator.

Discrete-time delta-sigma modulator with improved anti-aliasing at lower quantization rates

A modulated amplifier output enable control eliminates audible pops when enabling and disabling an audio amplifier output stage. The output of the audio amplifier is transitioned between an enabled state and a disabled state using a modulated control signal that enables and disables the output of the audio amplifier. Durations of the enabled state vs. the disabled state of the amplifier are adjusted to cause a transition between a fully disabled state and a fully enabled state of the audio amplifier so that the transition between the disabled state and the enabled state of the amplifier output is inaudible.

Modulated audio amplifier output enable control

A current-steering type digital-to-analog converter (DAC) is disclosed. The DAC includes a first sub-DAC, a second sub-DAC and a controlling device. Both the first sub-DAC and the second sub-DAC are configured to receive input signals. The controlling device selectively and periodically sends output signals of either the first sub-DAC or the second sub-DAC to a resistive load while sending output signals of the remaining one of the two sub-DACs to a dummy resistive load. An output of the DAC is provided at the resistive load.

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Austin, TX, United States of America

Robin Matthew Tsang