Digital sensors, electrical circuits and methods
The disclosure relates to microphone and other sensor assemblies having a transduction element and an integrated circuit. The integrated circuit includes a switched-capacitor delta-sigma analog-to-digital converter (ADC) including a first integrator stage having a switched-capacitor circuit and a first plurality of parallel amplifiers. A logic circuit coupled to the integrator circuit is configured to selectably disable a subset of enabled amplifiers of the first integrator stage during a first phase of operation and to re-enable the subset of disabled amplifiers during a second phase.
1. A sensor assembly comprising:
a transduction element configured to generate an electrical signal in response to detecting an environmental condition;
an integrated circuit comprising a delta-sigma analog-to-digital converter (ADC) coupled to the transduction element and configured to convert the electrical signal into a digital signal, the ADC comprising an integrator circuit including a first integrator stage comprising a switched-capacitor circuit (SCC) and a first plurality of amplifiers connected in parallel,
the first integrator stage having a first phase of operation during which charge sampling occurs and a second phase of operation during which charge redistribution occurs; and
a logic circuit coupled to the integrator circuit and configured to selectably disable a subset of enabled amplifiers of the first integrator stage during the first phase and to re-enable the subset of disabled amplifiers during the second phase.
2. The assembly of claim 1 , wherein the enabled amplifiers correspond to a number of enabled amplifiers required to satisfy a settling requirement of the ADC during the second phase.
3. The assembly of claim 2 , wherein the number of enabled amplifiers is based on an operating frequency of the ADC.
4. The assembly of claim 2 , wherein the number of enabled amplifiers is less than or equal to a number of amplifiers in the first plurality of amplifiers.
5. The assembly of claim 2 , wherein each of the first plurality of amplifiers are cascode transconductance amplifiers.
6. The assembly of claim 1 further comprising a switched-capacitor summer circuit comprising a plurality of amplifiers connected in parallel, the integrator circuit including a plurality of cascaded integrator stages, each integrator stage comprising a switched-capacitor circuit (SCC) and a plurality of amplifiers connected in parallel, wherein the output of each of the plurality of integrator stages is coupled to the switched-capacitor summer circuit.
7. The assembly of claim 6 , wherein the logic circuit is configured to selectably disable a subset of enabled amplifiers in each integrator stage and in the switched capacitor summer circuit during the first phase and to re-enable the subset of disabled amplifiers during the second phase.
8. The assembly of claim 7 , wherein each of the plurality of amplifiers are cascode transconductance amplifiers.
9. The assembly of claim 7 , wherein the enabled amplifiers correspond to a number of enabled amplifiers required to satisfy a settling requirement of the ADC during the second phase.
10. An integrated circuit for a sensor assembly, the integrated circuit comprising:
a delta-sigma analog-to-digital converter (ADC) configured to convert an electrical signal generated by a transconductance element of a sensor assembly into a digital signal when the integrated circuit is coupled to the transconductance element,
the ADC comprising an integrator circuit including a first integrator stage comprising a switched-capacitor circuit (SCC) and a first plurality of amplifiers connected in parallel, the first integrator stage having a first phase of operation during which charge sampling occurs and a second phase of operation during which charge redistribution occurs; and
a logic circuit coupled to the integrator circuit and configured to selectably disable a subset of enabled amplifiers of the first integrator stage during the first phase and to re-enable the subset of disabled amplifiers during the second phase.
11. The circuit of claim 10 further comprising a switched-capacitor summer circuit comprising a plurality of amplifiers connected in parallel, the integrator circuit including a plurality of cascaded integrator stages, each integrator stage comprising a switched-capacitor circuit (SCC) and a plurality of amplifiers connected in parallel, wherein the output of each of the plurality of integrator stages is coupled to the switched-capacitor summer circuit.
12. The circuit of claim 11 , wherein the enabled amplifiers correspond to a number of enabled amplifiers required to satisfy a settling requirement of the ADC during the second phase.
13. The circuit of claim 12 , wherein the number of enabled amplifiers is less than or equal to a number of amplifiers in the first plurality of amplifiers.
14. The circuit of claim 12 , wherein the logic circuit is configured to selectably disable a subset of enabled amplifiers in each integrator stage and in the switched capacitor summer circuit during the first phase and to re-enable the subset of disabled amplifiers during the second phase.
15. The circuit of claim 12 in combination with a sensor assembly comprising a transconduction element coupled to the ADC.
16. A method of operating a digital sensor assembly, the method comprising:
generating an electrical signal with a transconduction element upon detection of an environmental condition;
converting the electrical signal to a digital signal with a delta-sigma analog-to-digital converter (ADC) comprising a plurality of integrator stages having a switched-capacitor circuit and a plurality of parallel amplifiers, the converting including:
performing charge sampling in a first integrator stage during a first phase when a first subset of the plurality of parallel amplifiers of the first integrator stage are enabled; and
redistributing charge in the first integrator stage during a second phase when a second subset of the plurality of parallel amplifiers of the first integrator stage are enabled, wherein first subset has fewer enabled amplifiers than the second subset.
17. The method of claim 16 further comprising enabling the number of amplifiers in the second subset based on a settling requirement of the ADC during the second phase, wherein the first subset is a subset of the second subset.
18. The method of claim 17 , enabling the number of amplifiers in the second subset based on a sampling frequency of the ADC.
19. The method of claim 16 , summing an output of each of the plurality of integrator stages in a switched-capacitor summer circuit comprising a plurality of amplifiers connected in parallel, wherein a number of enabled amplifiers in the switched-capacitor summer circuit during the second phase is greater than a number of enabled amplifiers during the first phase.
20. The method of claim 16 , generating the electrical signal upon detection of an acoustic signal.