Capacitive touch system using both self and mutual capacitance

A system for detecting one or more touch events on a touch sensor, comprising:

• a touch sensor having a plurality of nodes defined by a plurality of first electrodes arranged in a first layer and a plurality of second electrodes arranged in a second layer;
• a pulse drive circuit operable to be coupled with one of said first electrodes;
• a capacitance detector unit operable to be connected with one of said second electrodes and configured to perform a capacitance measurement dependent on charging and/or discharging properties of a capacitance;
• wherein the system is configured to only use the capacitance detector for measuring a self capacitance of each of the plurality of second electrodes;
• and wherein the system is further configured to use the capacitance detector unit synchronized with said pulse drive circuit for measuring the mutual capacitance between said first and second electrodes, wherein the pulse drive circuit is driven to influence the charging and/or discharging of a measured capacitance provided by the capacitance detector.

A method for determining multiple touch events in a multi-touch sensor system having a touch sensor including a plurality of nodes defined by a plurality of first electrodes arranged in a first layer and second electrodes arranged in a second layer, wherein first and second layer are separated by an insulating layer, the method comprising:

• performing self capacitance measurements for at least two of the plurality of second electrodes using a capacitance detector;
• detecting one or more touch events as a result of the performed self capacitance measurements;
• performing a plurality of mutual capacitance measurements for only a subset of the nodes, wherein the subset is fewer than all of the nodes and includes at least the nodes corresponding to the touch events and wherein a mutual capacitance measurement is performed between first and second electrodes, wherein a pulse drive circuit is connected with one of said first electrodes and the capacitance detector is connected with one of said second electrodes and wherein the pulse drive circuit is synchronized with the capacitance detector, wherein a mutual capacitance measurement is based on charging and/or discharging of a measured capacitance and the pulse drive circuit is synchronized to influence the charging and/or discharging of the measured capacitance;
• and
• detecting two or more touch events as a result of the plurality of mutual capacitance measurements.