Integrated Device Technology, Inc.

Semtech Corporation

Input/output, Inc.

Jeffrey Blackburn

Ajaykumar A Kanji

Richard A Johnson

Ben William Jones

Chung-Kai Chow

Scott T Dupuie

Mark E Burchfield

Michael L Abrams

Roger Maher

Burton A Devolk

Frank Mayo

Mauricio Zavaleta

James Broseghini

An audio output circuit includes a port attenuation circuit, which is configured to convert an abrupt dc voltage offset transition between a pair of audio signals received in sequence at an input thereof into a more gradual transition. This conversion is achieved by performing, in sequence, a ramp-to-mute operation on a first of the pair of audio signals and a ramp-from-mute operation on a second of the pair of audio signals. The ramp-to-mute operation includes ramping an output of the audio output circuit from a dc voltage offset associated with the first of the pair of audio signals to a reference dc voltage offset. The ramp-from-mute operation includes ramping the output of the audio output circuit from the reference dc voltage offset to a dc voltage offset associated with the second of the pair of audio signals. These ramping operations may be performed using voltage steps having uniform step size.

Audio output circuits having ramped attenuation circuits that inhibit pop disturbances when audio sources are switched

Anti-pop circuits are provided for an audio amplifier that uses a power supply voltage and a ground voltage to drive a load with an audio signal that is centered about a virtual analog ground. These anti-pop circuits include a variable resistor and a capacitor that are connected to the audio amplifier to provide a low pass filter. The variable resistor has resistance that varies in response to a voltage level of the virtual analog ground, such as a difference between a voltage level of the power supply voltage and the voltage level of the virtual analog ground. The variable resistor may be a field effect transistor having a gate that is responsive to the differences between the voltage level of the power supply voltage and the voltage level of the virtual analog ground. The capacitor may be a field effect transistor, as well. Related methods are also described.

Anti-pop circuits and methods for audio amplifiers using variable resistors

An audio system includes a CODEC audio jack having left and right audio ports and a jack sense circuit. The jack sense circuit includes left and right amplifiers and a cross-drive impedance sensing circuit. This cross-drive impedance sensing circuit, which is electrically coupled to the left and right audio ports and the left and right amplifiers, detects the resistances of left and right output loads in order to determine characteristics of a device connected to the CODEC audio jack. The cross-drive impedance circuit is configured to measure a resistance of a left output load electrically coupled to the left audio port, in response to a 'right' test signal generated by the right amplifier, and is further configured to measure a resistance of a right output load electrically coupled to the right audio port in response to a 'left' test signal generated by the left amplifier.

Cross-drive impedance measurement circuits for sensing audio loads on CODEC channels

A system for acquiring environmental information measurements. The 5 system () utilize a sensor, () a front-end circuit, () a loop filter (), a switch controller (), and a reduced-order loop control circuit to provide reliable data measurements while providing robust system behavior. The system further includes a sensor simulator () for simulating the operation of the sensor () and testing the operation of the front-end circuit () and the loop filter ().

Sensor

Improved digital to analog converter (DAC) circuitry incorporating the ability to utilize a single DAC to generate either voltage or current outputs, and the ability to digitally adjust the gain and offset. Previous digital to analog circuitry has been limited to a single type of analog output per DAC and to the use of external precision resistors to set the gain and offset for a single DAC, or a group of DACs. By utilizing the same on-chip circuitry to supply both types of outputs, chip area, power consumption and cost is reduced while offering more flexibility to the customer. The ability to digitally adjust the gain and offset for a group of DACs eliminates the cost of external resistors, lowers the board area, and lowers the assembly cost for the end product. In addition, since gain and offset can be adjusted dynamically, maximum flexibility is provided to the customer. Digital adjustment of gain and offset can be used to calibrate for chip and system errors, and can allow more exact adjustment and external precision resistors.

Digital adjustment of gain and offset for digital to analog converters

A high-impedance mode is provided for an output of a precision measurement unit (PMU). The PMU includes an output amplifier that provides a forcing voltage or current to a device under test. When the high-impedance mode is activated, the output amplifier is decoupled from an output terminal of the PMU and the output amplifier is disabled. This prevents the voltage on the output terminal from rising in an uncontrolled manner, and prevents current spikes from forming on the output terminal when connected to a device under test. The high-impedance mode is deactivated to permit connection of the PMU to another device under test by re-coupling the output amplifier to the output terminal and enabling operation of the output amplifier.

Growing community of inventors

Austin, TX, United States of America

Jeffrey Blackburn