Capacitive field sensor with sigma-delta modulator
AssigneeCypress Semiconductor Corporation
InventorsAndriy Ryshtun, Victor Kremin
Life of this patent
Estimating the term…
Abstract
A capacitive sensor includes a switching capacitor circuit, a comparator, and a charge dissipation circuit. The switching capacitor circuit reciprocally couples a sensing capacitor in series with a modulation capacitor during a first switching phase and discharges the sensing capacitor during a second switching phase. The comparator is coupled to compare a voltage potential on the modulation capacitor to a reference and to generate a modulation signal in response. The charge dissipation circuit is coupled to the modulation capacitor to selectively discharge the modulation capacitor in response to the modulation signal.
Claims20
A method for determining a presence of an object, the method comprising:
- charging a first capacitor and a second capacitor during a first phase;
- discharging said first capacitor during a second phase;
- measuring a charge of said second capacitor;
- modulating a signal based on said charge of said second capacitor;
- determining based on a duty cycle of said signal whether an object is proximate to said first capacitor, wherein said duty cycle of said signal is asymmetrically responsive to noise and a presence of an object.
A capacitive sensor circuit, comprising:
- a modulation capacitor coupled with a sensing capacitor;
- a plurality of switches configured to charge the sensing capacitor and the modulation capacitor during a first phase, and discharge the sensing capacitor during a second phase;
- a modulator circuit coupled with the modulation capacitor and configured to modulate a signal based on an amount of charge stored on the modulation capacitor;
- a measurement circuit coupled with the modulator circuit, wherein the measurement circuit is configured to determine based on a duty cycle of said signal whether an object is proximate to said sensing capacitor, wherein said duty cycle of said signal is asymmetrically responsive to noise and a presence of the object, wherein during the second phase, wherein the plurality of switches are configured to couple the sensing capacitor to ground.
A capacitive sensor circuit, comprising:
- a modulation capacitor coupled with a sensing capacitor;
- a plurality of switches configured to charge the modulation capacitor based on a capacitance of the sensing capacitor;
- a modulation circuit coupled with the modulation capacitor and configured to generate a modulated signal having a duty cycle that changes in a first direction in response to a change in capacitance of the sensing capacitor and changes in a second direction in response to noise.
Dependencies are inferred from the claim text.