Position detection circuit, position detection method, and position detection system

A position detection circuit for detecting, by using a touch sensor of a mutual capacitance system, a position indicated by a passive pointer to a touch surface disposed on the touch sensor, the touch sensor including a plurality of first sensor electrodes and a plurality of second sensor electrodes, the first sensor electrodes intersecting the second sensor electrodes at a plurality of cross points, the position detection circuit comprising:

• a detection circuit which, in operation, detects a touch region of the touch surface, wherein a capacitance value at each of the cross points in the touch region is greater than or equal to a threshold value;
• a calculation circuit which, in operation, calculates a total value of a plurality of capacitance values at each of the cross points in a calculation region surrounding at least part of the touch region;
• and
• an output circuit which, in operation, outputs an indicated position that is indicated by a touch in the touch region detected by the detection circuit, based on the total value of the capacitance values calculated by the calculation circuit,
• wherein the output circuit, in operation, outputs the indicated position when the total value is equal to or less than a threshold value, and does not output the indicated position or invalidates the indicated position and outputs the indicated position that has been invalidated, when the total value exceeds the threshold value.