Parasitic Insensitive Sampling in Sensors

A sensor system subject to a variable parasitic capacitance, the sensor system comprising:

• a sensor comprising a sense capacitor with a variable sense capacitance, wherein when an input pressure is sensed by the sensor, the variable sense capacitance is modulated, thereby generating one or more digital output signals indicative of the input pressure;
• a readout circuit comprising a converter having an analog input connected to the sense capacitor, and
• an offset capacitor operatively charged and discharged out of phase with respect to the sense capacitor;
• wherein:
• the sensor system uses the offset capacitor, based on an auto-zeroing technique, to sample the analog input of the converter prior to a charging phase of the sensor system so that some effects of the variable parasitic capacitance on the one or more digital output signals are reduced.

A method of measuring pressure in presence of a variable parasitic capacitor, the method comprising:

• providing a sense capacitor with a variable sense capacitance;
• providing an offset capacitor;
• providing a readout circuit having an integrating capacitor;
• in an initial state
• configuring the offset capacitor to sample, based on an auto-zeroing techniques, an output of the readout circuit to compensate for the parasitic capacitance;
• in a charging phase following the initial state,
• storing first charges across the sense capacitor;
• and
• storing second charges across the offset capacitor;
• in an integration phase, transferring the first and the second charges to the integrating capacitor, thereby generating a readout circuit output signal in correspondence of an input pressure, and
• configuring the offset capacitor to center variations of the sense capacitor to a center of a full-scale of the readout circuit,
• wherein the storing the first and the second charges and the transferring the first and the second charges are performed such that a charging and discharging of the offset capacitor is out of phase with respect to the sense capacitor.