Patent ID: 9292137
Filing Date: 2016-03-22
CPC Classification: G06F

Claim Text:
1. A semiconductor device coupled to a first touch electrode group in a first direction and to a second touch electrode group in a second direction intersecting with said first direction, the two touch electrode groups configuring a touch panel, said semiconductor device comprising: a first detection circuit detecting whether stray capacitance of each of the touch electrodes configuring said first and said second touch electrode groups has increased compared with when said touch panel is not touched; a control circuit determining whether there is a multi-touch state in which the stray capacitance of a plurality of touch electrodes in said first touch electrode group and the stray capacitance of a plurality of touch electrodes in said second touch electrode group have increased; a voltage application circuit applying a voltage to the touch electrodes of which the stray capacitance has increased in said first touch electrode group when said multi-touch state is in effect; and a second detection circuit detecting a voltage change of each of the touch electrodes of which the stray capacitance has increased in said second touch electrode group when said voltage application circuit applies the voltage, wherein when said multi-touch state is in effect, said control circuit identifies a touched area over said touch panel based on the result of the detection by said second detection circuit, for detecting the stray capacitance of a given touch electrode in the first and second touch electrode groups, the first detection circuit detects a divided voltage of the given touch electrode when a predetermined voltage is applied to one of the ends of a first capacitive element of which the other end is serially coupled to the given touch electrode, for detecting the stray capacitance of the given touch electrode, the first detection circuit performs a precharging operation to precharge a second capacitive element coupled to the other end of the first capacitive element via a resistive element, after the precharging operation, the first detection circuit alternately performs a discharging operation and a detecting operation, the discharging operation fully discharging the given touch electrode, fully discharging the first capacitive element, and partially discharging the second capacitive element by coupling both ends of the first capacitive element to a ground node, the detecting operation detecting the divided voltage of the given touch electrode when the voltage of the second capacitive element is applied as the predetermined voltage to the other end of the first capacitive element, the first detection circuit includes a first counter configured to increment a first counter value every time a detected voltage of the given touch electrode exceeds a first predetermined reference voltage, during the detecting operation, the control circuit determines whether the stray capacitance of the given touch electrode has increased on the basis of the number of times the discharging operation is performed until the voltage of the given touch electrode drops below the predetermined first reference voltage, based on the first counter value of the first counter, when the first and second touch electrode groups each include touch electrodes having an increased stray capacitance, the second detection circuit applies a voltage to one of the touch electrodes of the first touch electrode group, and detects when a voltage of a corresponding touch electrode in the second electrode group exceeds a predetermined second reference voltage, the second detection circuit includes a second counter to increment a second counter value until the voltage of the corresponding touch electrode in the second electrode group exceeds the predetermined second reference voltage, and the control circuit determines where on the touch panel is touched, based on the second counter value of the second detection circuit.