Ratio-Metric Self-Capacitance-to-Code Convertor
AssigneeCypress Semiconductor Corporation
InventorAndriy Maharyta
Life of this patent
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Abstract
A circuit, system, and method for converting self capacitance to a digital value may include a pair of charge transfer circuits, each including a deadband switch network, a sensor capacitor or modulation capacitor, and an integration capacitor may be coupled to a comparator to produce a bitstream representative of the capacitance of the sensor capacitor of one of the charge transfer circuits. The bitstream may be used to indicate a capacitance value of the self capacitance through conversion by a digitizing circuit element.
Claims20
A capacitance-to-code converter comprising:
- a first charge transfer circuit comprising a sensor capacitor alternately coupled to first voltage potential and a first integration capacitor through a first deadband switch network;
- a second charge transfer circuit comprising a modulation capacitor alternately coupled to second voltage potential and a second integration capacitor through a second deadband switch network;
- a comparator circuit coupled to the first charge transfer circuit at the first integration capacitor and the second charge transfer circuit at the second integration capacitor, the comparator configured to output a bitstream;
- and
- a digitizer configured to convert the bitstream to a digital value representative of the a capacitance of the sensor capacitor.
(canceled)
A system comprising:
- at least one electrode comprising a capacitance that alterable by the proximity of a conductive object to the electrode;
- and
- a capacitance measurement circuit comprising:
- a first charge transfer circuit coupled to the at least one electrode and a first integration capacitor, the first charge transfer circuit comprising a first deadband switch network for alternately coupling the at least one electrode to a first voltage potential and the first integration capacitor;
- a second charge transfer circuit comprising a modulation capacitor and a second integration capacitor, the second charge transfer circuit comprising a second deadband switch network for alternately coupling the modulation capacitor to a second voltage potential and the second integration capacitor;
- a comparator comprising a first input coupled to the first charge transfer circuit at the first integration capacitor and a second input coupled to the second charge transfer circuit at the second integration capacitor, the comparator configured to output a bitstream;
- and
- a digitizer configured to convert the bitstream to a digital value representative of the a capacitance of the sensor capacitor.
A method of measuring capacitance comprising:
- accumulating charge on a first integration capacitor through a plurality of first charge transfer operations;
- accumulating charge on a second integration capacitor through a plurality of second charge transfer operations;
- generating a bitstream from a comparison of the first and second accumulated charges;
- and
- converting the bitstream to a digital value representative of a sensor capacitance, the sensor capacitance used in the first charge transfer operation.
Dependencies are inferred from the claim text.