Resistor based delta sigma multiplying DAC with integrated reconstruction filter
AssigneeSilicon Laboratories Inc.
InventorDinesh Babu Mugunthu Maheswaran
Life of this patent
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Abstract
A digital to analog converter that includes a delta sigma modulator coupled to receive a digital data. The delta sigma modulator supplies a multi-bit resistor digital to analog converter (DAC). The multi-bit resistor digital to analog converter supplies an amplifier with an analog signal corresponding to the digital data. A first low pass filter is coupled between the multi-bit digital to analog converter and the amplifier stage and filters out shaped quantization noise before it reaches the amplifier. A second low pass filter is coupled to an output of the amplifier stage and filters out residual quantization noise and chopping artifacts from the amplifier stage.
Claims20
An apparatus comprising:
- a phase-locked loop including a digital loop filter to supply a digital control signal;
- a digital to analog converter including,
- a delta sigma modulator coupled to receive the digital control signal from the digital loop filter and supply digital data after processing the digital control signal;
- a multi-bit digital to analog converter (DAC) with unit elements coupled to receive the digital data from the delta sigma modulator;
- an amplifier stage coupled to the multi-bit DAC;
- a first low pass filter coupled between the multi-bit DAC and the amplifier stage;
- and
- a second low pass filter coupled to an output of the amplifier stage and coupled to supply an analog signal.
A method comprising:
- generating a digital loop filter output signal in a digital loop filter of a phase-locked loop;
- supplying the digital loop filter output signal to a delta sigma modulator;
- generating a delta sigma modulator output signal based on the digital loop filter output signal;
- supplying the delta sigma modulator output signal to a multi-bit digital to analog converter (DAC);
- converting the delta sigma modulator output signal supplied to the multi-bit DAC to a first analog signal;
- filtering the first analog signal to remove high frequency components from the first analog signal in a first low pass filter and generating a filtered first analog signal and supplying the filtered first analog signal to an amplifier stage;
- providing gain to the filtered first analog signal in an amplifier stage and supplying a second analog signal from the amplifier stage;
- and
- filtering the second analog signal from the amplifier stage in a second low pass filter and supplying from the second low pass filter an output analog signal.
An apparatus comprising:
- an integrated circuit including,
- a phase-locked loop including,
- a phase and frequency detector;
- a digital loop filter coupled to the phase and frequency detector and supplying a digital control signal;
- a digital to analog converter including,
- a delta sigma modulator coupled to receive the digital control signal;
- a multi-bit digital to analog converter (DAC) coupled to receive an output of the delta sigma modulator;
- an amplifier stage coupled to the multi-bit digital to analog converter;
- a first low pass filter coupled between the multi-bit digital to analog converter and the amplifier stage;
- and
- a second low pass filter coupled to an output of the amplifier stage to supply an analog signal corresponding to the digital control signal;
- and
- a voltage controlled crystal oscillator coupled to the analog signal to supply a voltage controlled crystal oscillator output signal based on the analog signal.
Dependencies are inferred from the claim text.