Sigma-delta modulator apparatus and method of generating a modulated output signal
AssigneeFreescale Semiconductor, Inc.
InventorsHassan Ihs, Frederic Schrive
Life of this patent
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Abstract
A discrete time sigma-delta modulator apparatus for class-D operation comprises a feed-forward path having an input at one end thereof and an output at another end thereof. A first summation unit is coupled in the feed-forward path to a first integrator. A quantizer is coupled in the feed-forward path after the first integrator and a feedback path arrangement is coupled to an input of the first summation unit. A low pass filter is arranged in the feedback path arrangement so as only to drive the first integrator.
Claims20
A discrete time sigma-delta modulator apparatus for class-D operation, the apparatus comprising:
- a feed-forward path having an input at one end thereof and an output at another end thereof;
- a first summation unit coupled in the feed-forward path to a first switched capacitor integrator;
- a quantizer coupled in the feed-forward path after the first switched capacitor integrator;
- a feedback path coupled to an input terminal of the first summation unit;
- a low pass filter having an input terminal coupled to an output terminal of the quantizer, and an output terminal coupled to a load via the output of the feed-forward path and to the input terminal of the first summation unit via the feedback path;
- and
- wherein the apparatus has a modulator running frequency;
- wherein the low pass filter has a cut-off frequency, the cut-off frequency of the low pass filter being less than the modulator running frequency.
A method of generating a modulated output signal, the method comprising:
- receiving an input signal;
- providing a feed-forward path having an input and an output, the feed-forward path being provided by:
- a first summation unit coupled to a first switched capacitor integrator, the first switched capacitor integrator being coupled to a quantizer;
- applying the input signal to the feed-forward path so as to provide the modulated output signal at the output of the feed-forward path;
- and
- a modulator running frequency;
- feeding back a portion of the modulated output signal to an input of the first summation unit only;
- and
- low pass filtering the portion of the modulated output signal fed back to the input of the first summation unit, the low pass filtering being with respect to a cut-off frequency less than the modulator running frequency.
A discrete time sigma-delta modulator apparatus for class-D operation, the apparatus comprising:
- a feed-forward path between an input terminal and an output terminal of the apparatus;
- a summation unit coupled in the feed-forward path, the summation unit having an input terminal coupled to the input terminal of the apparatus, and an output terminal coupled to an input terminal of a switched capacitor integrator;
- a quantizer coupled in the feed-forward path, the quantizer having an input terminal coupled to an output terminal of the switched capacitor integrator, and an output terminal;
- a drive circuit coupled having an input terminal coupled to the output terminal of the quantizer, and an output terminal coupled to a load;
- a low pass filter in a feed-back path, the low pass filter having an input terminal coupled to the input terminal of the drive circuit, and an output terminal;
- and
- a feedback path coupled between the output terminal of the quantizer and the input terminal of the summation unit, wherein the apparatus has a modulator running frequency, and wherein the low pass filter has a cut-off frequency, the cut-off frequency of the low pass filter being less than the modulator running frequency.
Dependencies are inferred from the claim text.