Stmicroelectronics S.r.l.

Marvell International Limited

Marvellworld Trade Ltd.

Vittorio Colonna

Gabriele Gandolfi

Andrea Baschirotto

Paolo Cusinato

Rinaldo Castello

Francesco Rezzi

Antonio Liscidini

Marco Sosio

Alessandro Savo

Stefano Marchese

Michele Chiabrera

Davide Tonietto

Marco Bongiorni

Alessio Pelle

Alberto Demarziani

Giacomo Bernardi

Pietro Liguori

An apparatus includes a temperature sensor, a digitally-controlled capacitor and a processor. The temperature sensor is coupled to a crystal oscillator and configured to generate an input signal depending on a temperature of the crystal oscillator. The digitally-controlled capacitor is connected to the crystal oscillator and configured to receive a control signal and, based on the control signal, to control a frequency of an output signal generated by the crystal oscillator. The processor is configured to receive the input signal from the temperature sensor, to convert the input signal into the control signal based on parameters that characterize the crystal oscillator and the digitally-controlled capacitor, and to apply the control signal to the digitally-controlled capacitor.

Digitally-based temperature compensation for a crystal oscillator

Technologies are described to DC-couple an integrated amplifier system to a source that provides a signal with an unknown DC component, for example to DC-couple an integrated audio codec to an analog microphone. In one aspect, methods include receiving, by an amplifier, a signal having an unknown DC component, and issuing an amplified signal; low pass filtering, with respect to a cutoff frequency, by a feedback circuit coupled between an output of the amplifier and an input of the amplifier, the amplified signal issued at the output of the amplifier to generate a filtered signal having frequencies lower than the cutoff frequency; and injecting, by the feedback circuit, the filtered signal into the input of the amplifier to cancel the unknown DC component below the cutoff frequency.

Integrated amplifier system

An analog to digital converter including a low pass filter element, a quantizer, and a digital to analog converter provide in a feedback path. The low pass filter element is configured to filter an analog input signal. The quantizer is configured to receive an analog output signal that is based on the filtered analog input signal and convert the analog output signal to a digital output signal. The digital to analog converter is configured to generate an analog feedback signal based on the digital output signal and selectively inject or absorb current associated with the feedback path to reduce noise associated with the digital to analog converter. The analog feedback signal is combined with the analog input signal at an input of the low pass filter element.

Analog to digital converter with noise reducing feedback path

A filtering analog to digital converter (ADC) includes an integrator receiving at its input an analog input signal. A filtering capacitor at the input of the integrator filters out a large portion of out-of-band interferers in the analog input signal. The integrator produces an output that is quantized to produce a digital output. A feedback path between the quantizer output and the integrator input includes a digital to analog converter (DAC).

Continuous time sigma-delta ADC with embedded low-pass filter

A control system for the characteristic parameters of an active filter includes: a system for the determination of the technological distribution of the components that provides the information related to said technological distribution of the components; an elaboration system for said information related to said technological distribution of the components; an active filter including at least two programmable passive circuital elements receiving said information related to said technological distribution of the components; said elaboration system, being aware of the topology for said active filter, comprises means for determining the value for said at least two programmable passive circuital elements; means for correcting the value for said at least two programmable passive circuital elements according to the value of the information related to said technological distribution of the components; means for determining the programming values for said at least two programmable passive circuital elements.

Control system for the characteristic parameters of an active filter

A method of self-calibrating a modulator includes at least one integrator likely to incur a phase error may include reading a pulse response of the modulator, calculating a phase error parameter of the at least one integrator, and calibrating the phase error parameter. In addition, the calibration may provide a count of pulse response samples above suitable threshold values, as well as a change in the value of a capacitor associated with the integrator based upon the sample count.

Method for self-calibrating a phase integration error in a modulator

An input stage includes switched capacitors for analog-digital converters. The stage comprises a first switched capacitor circuit structure suitable for sampling an analog signal in input to the converter with a preset sampling period, a buffer having in input the analog signal and that can be connected to the first circuit structure by means of a first and a second sampling switch of the first circuit structure coupled respectively with the output terminal and the input terminal of the buffer. The first and the second switch are controlled respectively by a first and a second signal to close respectively for a first interval of time and for a successive second interval of time of a first semi-sampling period of the analog signal. The stage comprises a second switched capacitor circuit structure connected to a reference voltage and to the buffer and suitable for generating the second signal with a value of voltage greater in absolute value than the value of the analog signal for the duration of the second interval of time of the semi-sampling period.

Input stage with switched capacitors for analog-digital converters

A method for calibrating a frequency of a sigma&mdash;delta modulator having a go path that includes, in series, a resonator circuit and of an analog to digital conversion block, and a feedback path including a digital to analog conversion block, including the steps: a) applying an input pulse to the resonator circuit; b) measuring the oscillating frequency of the output signal from the resonator circuit in response to the pulse, while the feedback path of the sigma&mdash;delta modulator is opened; c) comparing the oscillating frequency of the resonator circuit with a selected frequency; d) modifying the oscillating frequency proportionately as a function of the comparison step. The resonator circuit includes an integrator filter with a variable gain amplifier in its feedback path, the variable gain configured to be modified as a function of the comparison, performed while the modulator feedback path is opened.

Method for self-calibrating a frequency of a modulator circuit, and circuit using said method

A sigma-delta-type converter comprises: a sigma-delta modulator having a digital output having a first prefixed bit number; a randomizer including a circular memory; an analogical reconstruction filter comprising a branch number equal to said first default number including sampling capacitors and a low-pass filter; characterized in that said circular memory comprises a number of elements equal to said first default number of bits less one and receives in input said first default number of bits less one, and in that a bit of said first default number of bits is applied to one of said branches of said reconstruction filter.

Randomizer for sigma-delta-type converter

Fully differential operational amplifier of the folded cascode type

A class AB single-stage operational amplifier having input decoupler stages for voltage signals, a voltage repeater stage, biasing transistors and bias current generators for the input decoupler stages, and capacitors placed between the input decoupler stages and the voltage repeater stage so as to increase the phase margin.

Class AB single-range advanced operational amplifier

Digital-analog converter comprising a third order sigma delta modulator

Current generator for alternatively providing a first constant current and a ratioed second constant current to a sigma-delta modulator

An integrated circuit has a first external supply terminal and a second external supply terminal for applying an external supply voltage to the circuit. The integrated circuit includes an analog unit supplied by at least one internal supply voltage derived from the external supply voltage, a low-pass filter connected to the first external supply terminal and to the second external supply terminal, and a driver connected between the low-pass filter and the analog unit for supplying the at least one internal supply voltage.

Integrated structure with an analog unit supplied by an external supply voltage by means of a low-pass filter and driving elements

An analog/digital &Sgr;&Dgr; converter has an input fed with an analog input signal, an output producing a digital signal representative of the analog input signal and a circuit for generating a dithering signal of amplitude adaptively regulated depending on the amplitude of the analog input signal. A comparator performs the regulation and uses a white noise dithering signal that is digitally generated and thereafter converted into an analog white noise dithering signal subjected to a second order filtering.

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Landriano, Italy

Vittorio Colonna