Patent ID: 9671899
Date: 2017-06-06
CPC Classifications: G06F

Claim:
1. A method for operating a touch panel display device comprising a first touch electrode group having a first plurality of touch electrodes and a second touch electrode group having a second plurality of touch electrodes, the method comprising: supplying, for a first duration of time during a charge period, a first current having a first current level to the first plurality of touch electrodes, wherein the first current causes a first touch voltage of the first touch electrode group to increase from a first initial voltage level to a first final voltage level over the first duration of time; supplying, for a second duration of time during the charge period, a second current having a second current level to the second plurality of touch electrodes, wherein the second current causes a second touch voltage of the second touch electrode group to increase from a second initial voltage level to a second final voltage level over the second duration of time, wherein the second current level differs from the first current level, and wherein the first current level, the first duration of time, the second current level, and the second duration of time are such that the first touch electrode group and the second touch electrode group are each charged to an approximately same touch voltage if a touch occurred in both the first touch electrode group and the second touch electrode group during the charge period, and are each charged to an approximately same non-touch voltage if the touch did not occur in either the first touch electrode group or the second touch electrode during the charge period; holding the first touch voltage for the first touch electrode group at a first held voltage level during a voltage hold period following the charge period; holding the second touch voltage for the second touch electrode group at a second held voltage level during the voltage hold period following the charge period; generating, during a compare period following the voltage hold period, a reference voltage that decreases from an initial reference level at a compare period start time to a final reference voltage level at a compare period end time; detecting a first period between the compare period start time and a first crossing time when the reference voltage drops below the first held touch voltage level; detecting a second period between the compare period start time and a second crossing time when the reference voltage drops below the second held touch voltage level; and comparing the first period and the second period to a threshold period to determine whether a touch occurred in each of the first touch electrode group and the second touch electrode group.