Method and apparatus for calibration of sensor signals

A sensing system comprising:

• a capacitative sensor;
• a reference sensor;
• a clock generator,
• an integration circuit, the integration circuit coupled to the capacitative sensor and the reference sensor, the integration circuit comprising a plurality of switches controlled by the clock generator to selectively combine a gain component and an offset component with outputs from the capacitative sensor and the reference sensor to generate an integrated output;
• a gain circuit, the gain circuit receiving the integrated output to combine a gain compensation therewith, the gain circuit including a resistor having a low temperature coefficient characteristic;
• wherein the gain circuit provides an output, Vout, obeying the following equation:
• Vout=Vdd*(1/β*(Cp−αR*Cr)/Cp)
• where:
• Cp is a measured capacitance from the capacitive sensor;
• Cr is a reference capacitance from the reference capacitor;
• αR is an offset component;
• R is a gain component;
• and
• Vdd is a supply voltage.

A method for providing calibration of sensor signals comprising a measuring sensor signal and a reference sensor signal, the method comprising:

• a) receiving a first signal integrating a charge difference from the measuring sensor signal and the reference sensor signal;
• b) receiving a second signal integrating a sequence of charge differences of the measuring sensor signal and the reference sensor signal based on the first signal;
• and,
• c) providing a feedback signal to the first stage, wherein the feedback signal includes the second signal and a gain characteristic.

A system for providing calibration of sensor signals comprising a measuring sensor and a reference sensor, the system comprising:

• a first integration stage circuit for generating a first signal integrating a charge difference from the measuring sensor and the reference sensor;
• and,
• a second integration stage circuit for generating a second signal integrating a sequence of charge differences of the measuring sensor signal and the reference sensor signal based on the first signal;
• wherein the first integration stage circuit receives a feedback signal comprising the second signal and a gain characteristic.

A method for providing calibration of sensor signals comprising a measuring sensor signal and a reference sensor signal, the method comprising:

• a) generating a plurality of integrated charge difference signals, wherein each integrated charge difference signal is an integrated charge difference between the measuring sensor signal and the reference sensor signal;
• b) integrating the plurality of integrated charge difference signals;
• and,
• c) providing a feedback signal comprising the integrated plurality of integrated charge difference signals and a gain characteristic.