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US 2009/0153152 A1Published application
Compensation circuit for a tx-rx capacitive sensor
AssigneeCypress Semiconductor Corporation
InventorsAndriy Maharyta, Viktor Kremin
Life of this patent
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Abstract
A capacitive sensor may include a transmit electrode and a receive electrode capacitively coupled with the transmit electrode. A capacitance sensing circuit senses a capacitance between the transmit and receive electrodes by applying a signal to the transmit electrode and rectifying a current waveform induced at the receive electrode. A compensation circuit reduces the effect of a mutual and parasitic capacitances of the transmit and receive electrode pair by adding a compensation current to the rectified current.
Claims20
An apparatus, comprising:
- a capacitive sensor including a transmit electrode and a receive electrode, wherein the receive electrode is capacitively coupled with the transmit electrode;
- a signal generator coupled with the transmit electrode and configured to generate an induced current waveform at the receive electrode by applying a transmit signal to the transmit electrode;
- a demodulation circuit coupled with the receive electrode, wherein the demodulation circuit is configured to output a rectified current based on the induced current waveform;
- and
- a compensation circuit coupled with the demodulation circuit, wherein the compensation circuit is configured to add a compensation current to the rectified current to generate a compensated current waveform.
2 more elements
A method, comprising:
- applying a transmit signal to a transmit electrode capacitively coupled to a receive electrode to generate an induced current waveform at the receive electrode;
- rectifying the induced current waveform to generate a rectified current;
- and
- adding a compensation current to the rectified current to generate a compensated current waveform.
1 more element
An apparatus, comprising:
- means for generating an induced current waveform based on a capacitance value of a capacitive sensor;
- means for generating a rectified current based on the induced current waveform;
- and
- means for generating a compensated current waveform by adding a compensation current to the rectified current.
1 more element
Dependencies are inferred from the claim text.