Compensation for variations in a capacitive sense matrix
AssigneeSTMicroelectronics Asia Pacific Ltd.
InventorsYannick Guedon, Sze-Kwang Tan, Dianbo Guo
Life of this patent
Estimating the term…
Abstract
A readout device for a capacitive sense matrix includes a computer readable storage medium configured to store capacitance data. The capacitance data represents capacitance values of the capacitive sense matrix. The readout device also includes a readout circuit configured to receive a signal from the capacitive sense matrix, the readout circuit being configured based upon the capacitance data. Also described are a readout method and a method of compensating for variations in capacitance.
Claims19
A readout device for a capacitive sense matrix including a capacitive intersection associated with a force node and a sense node, wherein said force node is configured to receive a drive signal, comprising:
- a differential amplifier having an input and an output, wherein said input is coupled to the sense node;
- a first capacitor coupled between the input and output of the differential amplifier;
- and
- a series connection of an inverter and a second capacitor coupled between said force node and said input of the differential amplifier;
- wherein said second capacitor comprises a variable capacitor having a variable capacitance value.
A readout device for a capacitive sense including a capacitive intersection associated with a force node and a sense node, wherein said force node is configured to receive a drive signal, comprising:
- a capacitor, different from the capacitive intersection, coupled to the force node and having a variable capacitance set by value obtained from capacitance data representing an expected capacitance of the capacitive intersection;
- and
- an integration circuit having an input configured to receive a first signal from the capacitive intersection and configured to receive a second signal from the capacitor having the variable capacitance value, the integration circuit operating to determine a difference between the first and second signals and generate an output signal as a function of both a sensed capacitance at the capacitive intersection as indicated by the first signal and the expected capacitance as indicated by the second signal.
A readout device for a capacitive sense matrix including a plurality of first capacitors each comprised of a capacitive intersection associated with a force node and a sense node, wherein said force node is configured to receive a drive signal, comprising:
- a memory configured to store capacitance data representing an expected capacitance value of one or more of the first capacitors of the capacitive sense matrix;
- a differential amplifier having an input and an output, wherein said input is coupled to the sense node;
- a first capacitor coupled between the input and output of the differential amplifier;
- a series connection of an inverter and a second capacitor between said force node and said input of the differential amplifier;
- wherein said second capacitor is different from any of the first capacitors of the capacitive sense matrix;
- and
- wherein said second capacitor comprises a variable capacitor having a variable capacitance set by the capacitance data representing the expected capacitance value of one or more of the first capacitors of the capacitive sense matrix stored in the memory.
Dependencies are inferred from the claim text.