Cirrus Logic Inc.

Morgan Timothy Prior

John Paul Lesso

Robert David Rand

John Bruce Bowlerwell

Yanto Suryono

Mark James Mccloy-Stevens

Xin Zhao

Pradeep Saminathan

Mehul Mistry

Anindya Bhattacharya

David Paul Singleton

Ivan Perry

Jonathan Timothy Wigner

Qi Cai

Christopher M Dougherty

Christopher P Mortimore

Ishita Samanta

Johnny Klarenbeek

This application relates to methods and apparatus for delay locked loops (DLLs). A DLL circuit includes a variable delay line, a phase detector and a delay controller. The DLL circuit is operable in a DLL mode in which a reference clock signal is input to the variable delay line and the delay controller controls a delay setting to achieve phase lock between the reference signal and an output signal. The DLL circuit is also operable in a frequency-locked-loop (FLL) mode, in which part of variable delay line is configured as a controlled oscillator to provide an oscillator signal, a frequency monitor determines a frequency relationship between the reference clock signal and the oscillator signal and the delay controller controls the delay setting to achieve frequency lock. The DLL circuit may configured to operate in the frequency-locked-loop mode on start-up and then transition to the DLL mode.

Delay locked loops

This application relates to audio driving circuitry (), and in particular to audio driving circuitry for outputting first and second audio driving signals for driving a stereo audio load (), which may be a stereo audio load of an accessory apparatus () removably coupled to the audio driving circuitry in use. A load monitor () is provided for monitoring to monitor, from a monitoring node (), an indication of a common mode return current passing through a common return path, together with an indication of a common mode component of the first and second audio driving signals and to determine an impedance characteristic of the stereo audio load. The load monitor () can provide dynamic monitoring of any significant change in load impedance. In some embodiments the load monitor () comprises an adaptive filter () which adapts a parameter of the filter which is related to the load impedance so as to determine the indication of load impedance.

Load detection

Class D amplifier circuitry comprising: input buffer circuitry configured to receive a first digital input signal modulated according to a first modulation scheme in which the digital input signal can take a first plurality N of discrete signal levels; analog modulator circuitry configured to generate an analog modulated signal based on an analog output signal output by the input buffer circuitry; and quantizer circuitry configured to generate an output signal based on the analog modulated signal, wherein the output signal is modulated according to a second modulation scheme in which the output signal can take a second plurality M of discrete signal levels, wherein the second plurality M is greater than the first plurality N.

Class D amplifier circuitry

An apparatus for providing an output signal to an audio transducer comprises: one or more signal paths for receiving respective digital audio input signals, applying respective digital gains, and outputting respective amplified digital audio input signals; one or more inputs for receiving one or more volume parameters associated with the digital audio input signals; converter circuitry, coupled to the one or more signal paths, for converting the one or more amplified digital audio input signals into the analogue domain, and outputting an analogue audio input signal; an analogue gain element, for applying an analogue gain to the analogue audio input signal and outputting the output signal; and a control circuit, coupled to the one or more signal paths, operative to select the analogue gain based on a comparison of the volume parameters and the one or more digital audio input signals as multiplied by the volume parameters, and to select the respective digital gains for each digital audio input signal so that an overall gain in the respective signal path corresponds to a volume parameter associated with the respective digital audio input signal.

Systems, apparatus and methods for dynamic range enhancement of audio signals

This application relates to methods and apparatus for audio signal processing, for example by a codec. An audio signal processing module has at least one input for receiving first and second input signals and an output path for outputting an output audio signal. The first and second input signals may be supplied by a first audio component and may correspond to the same source audio data. A controller is configured to compare the first and second input signals and to select one of the first or second input signals as the basis for a signal to be supplied to said output path based on the comparison. The controller may determine a measure of similarity in content between the first and second input signals.

Audio signal processing

This application relates to methods and apparatus for audio signal processing, for example by a codec. An audio signal processing module () has at least one input () for receiving first and second input signals (Din, Din) and an output path for outputting an output audio signal (Vout). The first and second input signals may be supplied by a first audio component () and may correspond to the same source audio data. A controller () is configured to compare the first and second input signals and to select one of the first or second input signals as the basis for a signal to be supplied to said output path based on the comparison. The controller may determine a measure of similarity (Sim) in content between the first and second input signals.

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Edinburgh, United Kingdom

Morgan Timothy Prior