Cirrus Logic Inc.

Jeff W Baumgartner

John Christopher Tucker

Gautham Devendra Kamath

Zhong You

Jieren Bian

Hua Hong

An integrated circuit audio processor having an internal-oscillator generated intermediate frequency reference provides for operation of an audio processor without requiring an external master clock. Input audio streams are sample-rate converted to an intermediate sample rate derived from the internal oscillator, which may be an LC oscillator. One or more output audio streams are generated from the one or more input audio streams at the intermediate sample rate and are converted from the intermediate sample rate to corresponding output sample rates. A divider generates the intermediate sample rate from the oscillator output, and is programmed to control the intermediate sample rate to ensure that the intermediate sample rate is in the proper range for operation of the integrated circuit. The divider can be programmed to accommodate changes in process, voltage and/or temperature of the IC, so that the intermediate sample rate is maintained near an expected frequency.

Audio processor with internal oscillator-generated audio intermediate frequency reference

A signal processing system includes a phase-locked loop to provide an output signal used, for example, as a delta sigma modulator operating clock signal. In at least one embodiment, a frame clock that provides synchronization for one or more blocks of data is used by the phase-locked loop as a reference signal. Utilizing the frame clock as the reference signal allows the signal processing system to reduce the number of clock signals present in the signal processing system. In another embodiment, a phase-locked loop includes a loop filter that utilizes a sample and reset circuit, a feed forward integrator, and a feed forward stabilizer to provide a low frequency phase-locked loop bandwidth. In at least one embodiment, the feed forward integrator amplifies capacitance of the sample and reset circuit, which reduces the size of loop filter capacitors and, thus, allows on-chip capacitor integration.

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Austin, TX, United States of America

Jeff W Baumgartner