Direct conversion of capacitive sensors with sampled voltage noise cancelation
AssigneeSTMicroelectronics International N.V.
InventorsRoberto MODAFFARI, Paolo PESENTI
Life of this patent
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Abstract
A capacitive sensing circuit includes a switched capacitor charge to voltage (C2V) converter circuit having an input coupled to a capacitive sensor and configured to receive a negative feedback signal. An offset and low-frequency noise cancelation circuit has an input coupled to an output of the switched capacitor C2V converter circuit. A sigma-delta analog-to-digital converter (ΣΔ-ADC) circuit includes a loop filter coupled to an output of the offset and low-frequency noise cancelation circuit, a quantizer coupled to an output of the loop filter and configured to generate a digital signal, and a digital-to-analog converter circuit configured to generate the negative feedback signal from the digital signal.
Claims20
A capacitive sensing circuit, comprising:
- a switched capacitor charge to voltage (C2V) converter circuit having an input coupled to a capacitive sensor and configured to receive a negative feedback signal;
- an offset and low-frequency noise cancelation circuit having an input coupled to an output of the switched capacitor C2V converter circuit;
- and
- a sigma-delta analog-to-digital converter (ΣΔ-ADC) circuit including a loop filter coupled to an output of the offset and low-frequency noise cancelation circuit, a quantizer coupled to an output of the loop filter and configured to generate a digital signal, and a digital-to-analog converter circuit configured to generate the negative feedback signal from the digital signal.
A method, comprising:
- generating a difference signal between a capacitive sensor output signal and a feedback signal;
- performing offset and low-frequency noise cancelation on the difference signal to generate a first signal;
- filtering the first signal to generate a second signal;
- quantizing the second signal to generate a digital signal;
- and
- performing a digital to analog signal conversion to convert the digital signal to generate the feedback signal.
Dependencies are inferred from the claim text.