A touch screen controller includes input circuitry receiving touch data from the touch screen. Processing circuitry acquires touch data from the input circuitry in a self-capacitance sensing mode, locates a force island and locates a sense island. A length of the force island and a length of the sense island is calculated. If the length of the force island is greater than a threshold force length and if the length of the sense island is greater than a threshold sense length, then the product of the lengths is calculated, and if greater than a threshold size, designated a valid area. Touch data in the valid area is then acquired in mutual-capacitance sensing mode, and represents palm touch if a maximum strength value in the valid area is less than a maximum area threshold and if a minimum strength value in the valid area is greater than a minimum area threshold.