An apparatus and method for converting a capacitance measured on a sensor element to a digital code. The apparatus may include a switching capacitor as a sensor element of a sensing device, and a sigma-delta modulator coupled to the sensor element to convert a capacitance measured on the sensor element to a digital code. The switching capacitor is in a feedback loop of the sigma-delta modulator. The method may include measuring a capacitance on a sensor element of a sensing device using a sigma-delta modulator, and converting the capacitance measured on the sensor element to a digital code.

Capacitance to code converter with sigma-delta modulator

A method for locating a conductive object at a touch-sensing surface may include detecting a first resolved location for the conductive object at the touch-sensing surface based on a first scan of the touch-sensing surface, predicting a location for the conductive object, and determining a second resolved location for the conductive object by performing a second scan of a subset of sensor elements of the touch-sensing surface, wherein the subset of sensor elements is selected based on the predicted location of the conductive object.

Predictive touch surface scanning

A switch circuit and method is described. In one embodiment, the switch circuit is configured to couple each of a plurality of plurality of capacitive sense elements and a plurality of capacitance sensors in different modes. In a first mode, the switch circuit is configured to couple each of the plurality of capacitance sensors to a group of two or more of the plurality of capacitive sense elements. In a second mode, the switch circuit is configured to couple the plurality of capacitance sensors to individual ones of the two or more of the plurality of capacitive sense elements in one of the groups.

Apparatus and method for reducing average scan rate to detect a conductive object on a sensing device

A capacitive sensor device comprises a first sensor electrode, a second sensor electrode, and a processing system coupled to the first sensor electrode and the second sensor electrode. The processing system is configured to acquire a first capacitive measurement by emitting and receiving a first electrical signal with the first sensor electrode. The processing system is configured to acquire a second capacitive measurement by emitting and receiving a second electrical signal, wherein one of the first and second sensor electrodes performs the emitting and the other of the first and second sensor electrodes performs the receiving, and wherein the first and second capacitive measurements are non-degenerate. The processing system is configured to determine positional information using the first and second capacitive measurements.

Capacitive sensor device

A method of operating a touch-sensing surface may include performing a first scan of a first set of electrodes of a touch-sensing surface, determining a presence of at least one conductive object proximate to the touch-sensing surface, in response to determining the presence of the at least one conductive object, performing a second scan of a second set of electrodes of the touch-sensing surface, and repeating the performing the second scan until the at least one conductive object is no longer proximate to the touch-sensing surface.

Dynamic mode switching for fast touch response

A circuit and method are given, which realizes a stable yet sensitive differential capacitance measuring device with good RF-suppression and with very acceptable noise features for use in capacitive sensor evaluation systems. By evaluating the difference of capacitor values only—with the help of a switched capacitor front-end—large spreads of transducer capacitor values are tolerable. Furthermore a mode of operation can be set up, where no essential galvanic connection between sensor input and the active read-out input at any given time is existing. The solution found exhibits a highly symmetrical construction. Using the intrinsic advantages of that solution the circuit of the invention is manufactured as an integrated circuit with standard CMOS technology at low cost.

Horst Knoedgen

Papers

Differential capacitance measurement