Analog-to-digital conversion circuit
AssigneeNuvoton Technology Corporation Japan
InventorHitoshi Kobayashi
Life of this patent
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Abstract
An analog-to-digital conversion circuit includes: a variable gain amplifier; a delta-sigma modulator that modulates an output of the variable gain amplifier to a pulse density modulation (PDM) signal; and a decimation filter that downsamples the PDM signal to output a first digital signal that is converted into a multi-bit digital signal. The decimation filter includes: a weight change unit that converts the PDM signal into a second digital signal that is weighted by multiplying a weight of the PDM signal by a reciprocal of an amplification factor of the variable gain amplifier; and a first digital filter that receives the second digital signal as an input, and outputs the first digital signal.
Claims9
An analog-to-digital conversion circuit comprising:
- a variable gain amplifier;
- a delta-sigma modulator that modulates an output of the variable gain amplifier to a pulse density modulation (PDM) signal;
- and
- a decimation filter that downsamples the PDM signal to output a first digital signal that is converted into a multi-bit digital signal, wherein
- the decimation filter includes:
- a weight change unit that converts the PDM signal into a second digital signal that is weighted by multiplying a weight of the PDM signal by a reciprocal of an amplification factor of the variable gain amplifier;
- and
- a first digital filter that receives the second digital signal as an input, and outputs the first digital signal,
- the analog-to-digital conversion circuit further comprises a gain controller that changes the amplification factor based on a value of the first digital signal, and
- the gain controller changes the amplification factor as follows:
- (i) when an absolute value obtained by multiplying the value of the first digital signal by the amplification factor is greater than a first reference level, the amplification factor is halved;
- and (ii) when the absolute value is less than a second reference level that is less than half the first reference level, the amplification factor is doubled.
An analog-to-digital conversion circuit comprising:
- a variable gain amplifier;
- a delta-sigma modulator that modulates an output of the variable gain amplifier to a pulse density modulation (PDM) signal;
- and
- a decimation filter that downsamples the PDM signal to output a first digital signal that is converted into a multi-bit digital signal, wherein
- the decimation filter includes:
- a weight change unit that converts the PDM signal into a second digital signal that is weighted by multiplying a weight of the PDM signal by a reciprocal of an amplification factor of the variable gain amplifier;
- and
- a first digital filter that receives the second digital signal as an input, and outputs the first digital signal,
- the first digital filter includes:
- a second digital filter that receives the second digital signal as an input, and outputs a fourth digital signal having a total number of bits less than a total number of bits of the first digital signal;
- and
- a third digital filter that receives the fourth digital signal as an input, and outputs the first digital signal,
- the analog-to-digital conversion circuit further comprises a gain controller that changes the amplification factor based on a value of the fourth digital signal, and
- the gain controller changes the amplification factor as follows:
- (i) when an absolute value obtained by multiplying the value of the first digital signal by the amplification factor is greater than a first reference level, the amplification factor is halved;
- and (ii) when the absolute value is less than a second reference level that is less than half the first reference level, the amplification factor is doubled.
Dependencies are inferred from the claim text.