Methods and systems for detecting a capacitance using switched charge transfer techniques

A method for measuring a measurable capacitance, the method comprising the steps of:

• applying a pre-determined voltage to the measurable capacitance;
• and
• allowing the measurable capacitance to share charge through a passive impedance with a filter capacitance, wherein the passive impedance remains coupled to both the measurable capacitance and the filter capacitance throughout the applying and allowing steps;
• and
• determining a value of the measurable capacitance as a function of a voltage on the filter capacitance.

A device for measuring a measurable capacitance, the device comprising:

• a filter capacitance means for storing charge;
• means for applying a pre-determined voltage to the measurable capacitance;
• passive impedance means statically coupled to both the measurable capacitance and the filter capacitance means for allowing the measurable capacitance to share charge with the filter capacitance means;
• and
• means for determining a value of the measurable capacitance as a function of a representation of a charge on the filter capacitance means.

A circuit for measuring a measurable capacitance at a first electrical node, the circuit comprising:

• a passive impedance statically coupled between the first electrical node and a second electrical node;
• a filter capacitance coupled between the second electrical node and a third electrical node;
• and
• a controller coupled to the first electrical node, wherein the controller is configured to perform a charge transfer process for a number of times greater than one, wherein the charge transfer process comprises applying a pre-determined voltage to the first electrical node for a period of time and allowing the measurable capacitance to share charge with the filter capacitance through the passive impedance, and wherein the controller is further configured to determine a value of the measurable capacitance as a function of a voltage on the filter capacitance and the number of times.

A proximity sensor comprising:

• a sensor electrode having a measurable capacitance;
• a switch coupled to the measurable capacitance;
• a passive network coupled to the measurable capacitance and the switch, the passive network comprising a passive impedance and a filter capacitance, wherein the passive impedance statically couples the measurable capacitance to the filter capacitance;
• and
• a controller coupled to the switch, wherein the controller is configured to perform a charge transfer process for a number of times greater than one, wherein the charge transfer process comprises applying a pre-determined voltage to the measurable capacitance using the switch and allowing the measurable capacitance to share charge with the filter capacitance through the passive impedance, and wherein the controller is further configured to determine a value of the measurable capacitance as a function of a representation of a charge of the filter capacitance and the number of times.