Stmicroelectronics S.r.l.

Antonio Grosso

Edoardo Botti

Cristiano Meroni

Marco Masini

Mauro Cleris

A digital-to-analog converter (DAC) for an audio system may include at least first and second subsets of individually selectable elementary current sources for delivering analog output current contributions, a code conversion circuit for selecting elementary current sources of first and second subsets as a function of codes of a pulse code modulated (PCM) input signal. The DAC may multiply by a certain factor incoming codes of the PCM signal after their value has remained lower than a threshold for a certain period of time and for as long as their value equals or surpasses the threshold value, and may correspondingly scale and de-scale by the same factor the amplitude of the analog output current contributions produced by the elementary current sources of the two subsets.

Enhancement of the dynamic range of a multibit digital-to-analog converter

There is provided an adjustable harmonic distortion detector that includes a clock signal source, means for the detection of a first period of evaluation, and means for the detection of a second period of evaluation. The detector has the characteristic that a first block memorizes a number equal to the clock pulses present in the first period of evaluation, a multiplier block performs a multiplication between the number stored in the first block and a multiplicative factor during the second period of evaluation, and a second block memorizes the outcome. The second block is adapted to generate an output signal when the outcome in the second block is equal to zero.

Adjustable harmonic distortion detector and method for using the same

A digital input PWM power amplifier includes an oversampling and noise shaping circuit receiving pulse code modulated (PCM) digital input data organized in words of a first number of M bits at a bit rate, and outputting PCM digital data organized in words of a smaller number of N bits at a multiple bit rate. A first bus transmits a first number of most significant bits (MSB) of the N bit words output from the oversampling and noise shaping circuit, and a second bus transmits a second number of least significant bits (LSB) of the N bit words output from the oversampling and noise shaping circuit. First and second PCM/PWM converters are respectively fed with the first and second number of bits transmitted through the first and second buses. The PWM signal output by the first converter is summed to an attenuated PWM signal output by the second converter on the inverting input node of the output power stage.

PWM power amplifier with digital input

A power amplification apparatus receiving in input an enable signal (En) and an input square wave signal (C) is described. The apparatus comprises a device ( ) receiving the input square wave signal (C) and the enable signal (En) and which produces a new enable signal (Ens) of the apparatus which is synchronized with a rise or down front of the input square wave signal (C), so that an output square wave signal (Vo) of the apparatus, which is normally shifted of a certain period fraction with respect to the square wave signal (C) in input to the apparatus, has the first (Ti) and the last (Tf) pulses which have a duration equal to a period fraction of the output square wave signal (Vo).

Power amplification equipment

A PWM power amplifier having at least one PCM/PWM converter fed by PCM digital input signals and producing PWM digital output signals, and at least one power amplification final stage of the PWM digital output signals. At least one PCM/PWM converterincludes a counter fed with at least one clock signal produced by a clock generator device and having a digital comparator suitable for comparing the PCM digital input signals of at least one PCM/PWM converter with a digital comparison signal produced by the counter and producing in output the PWM digital signals. The clock generator device includes a pulse generator device and an oscillator; the pulse generator device receives a signal at a frequency that is equal to the frequency of the PCM digital input signals of the at least one PCM/PWM converter and produces in output reset pulses. The reset pulses are sent in input to the oscillator, which produces in output the at least one clock signal.

PWM power amplifier

A low frequency PWM output bridge amplifier having an input network configurable for standard PWM digital input signals, phase shift PWM digital input signals or analog input signals and for standard PWM output or phase shift PWM output is provided. The amplifier includes two identical amplifying modules. One for the amplifying channel relative to the direct or positive PWM output and the other for the amplifying channel relative to the inverted or negative PWM output. Each module includes a switching output operational amplifier, having a voltage mode noninverting input, a current mode inverting input and a loop filter implementing a single or multiple slope integrator outputting a signal of a substantially triangular waveform. Each module also includes a logic inverter or a cascade of logic inverters coupled in cascade to the output of the integrator and outputting a logic PWM signal, an output power stage converting the logic PWM signal output by the inverter(s) in a PWM signal, switching between the potentials of the two supply rails of the circuit, and a feedback resistor connecting the output of power stage to the inverting input of the operational amplifier.

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Milan, Italy

Antonio Grosso