Cirrus Logic Inc.

Silicon Laboratories Inc.

Silicon Labs Cp, Inc.

Kartika Prihadi

Kenneth Wilson Fernald

Golam Rasul Chowdhury

Bryan Garnett Cope

Mark Alexander

Krishnan Subramonium

Axel Thomsen

Eric J Swanson

Robert Thomas Grisamore

Karl I Nordling

A precision oscillator for an asynchronous transmission system. An integrated system on a chip with serial asynchronous communication capabilities includes processing circuitry for performing predefined digital processing functions on the chip and having an associated on chip free running clock circuit for generating a temperature compensated clock. An on-chip UART is provided for digitally communicating with an off-chip UART, which off-chip UART has an independent time reference, which communication between the on-chip UART and the off-chip UART is effected without clock recovery. The on-chip UART has a time-base derived from the temperature compensated clock. The temperature compensated clock provides a time reference for both the processing circuitry and the on-chip UART.

Precision oscillator for an asynchronous transmission system

A precision oscillator for an asynchronous transmission system. An integrated system on a chip with serial asynchronous communication capabilities includes processing circuitry for performing predefined digital processing functions on the chip and having an associated on chip free running clock circuit for generating a temperature compensated clock. An asynchronous on-chip communication device is provided for digitally communicating with an off-chip asynchronous communication device, which off-chip asynchronous communication device has an independent time reference, which communication between the on-chip communication device and the off-chip asynchronous communication device is effected without clock recovery. The asynchronous on-chip communication device has a time-base derived from the temperature compensated clock. The temperature compensated clock provides a time reference for both the processing circuitry and the asynchronous on-chip communication device.

An attenuator includes a first stagehaving a first operational amplifierand a tapped resistor. Tapped resistorhas an input for receiving input data, an output coupled to an output of first operational amplifier, and a plurality of taps for selectively presenting a sequence of voltages to a noninverting input of first operational amplifier. Each of these sequences of voltages corresponds to an attenuation step such that first stagesteps the attenuation produced by the attenuator from an intermediate value to a predetermined ending value. A second stageincludes a second operational amplifierand a tapped resistor. Tapped resistorincludes an input for receiving analog data from first stage, an output coupled to an output of second operational amplifier, and a plurality of taps for selectively presenting a sequence of voltages to a noninverting input of operational amplifier. Each of the sequence of voltages corresponds to an attenuation step, a second stagestepping the attenuation from a predetermined starting value to the intermediate value.

Multiple stage attenuator

An interface for coupling a modem port with a transmission line includes a hybrid converter having a variable gain amplifier coupling a transmit path of a first differential polarity and a received path of a second differential polarity.

System and methods for modem interface

Audio data processing circuitry,includes a plurality of analog inputs,for receiving analog audio data and a digital input,for receiving digital audio data. A analog mixer,mixes analog data received at said plurality of analog inputs,to generate a mixed analog audio stream. An analog-to-digital converter,converts the mixed analog audio stream to a digital audio stream and a digital mixer,mixes digital data received at the digital input,with the digital audio stream from the analog mixer,to generate a mixed digital audio stream.

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Austin, TX, United States of America

Kartika Prihadi