Abstract: An apparatus detects the approach and touch-down of an object relative to a sensor panel. The apparatus includes a digital filter for determining a first derivative of a current flow in the sensor panel and a controller determines when the first derivative reaches a maximum. In a preferred embodiment, a magnitude for current flow in a plurality of corners of the sensor panel is determined by the controller. These magnitudes are then summed to determine a current flow from which the first derivative is computed. The current flow is analyzed by the controller to determine when an object is approaching the sensor panel, has contacted the sensor panel, and is withdrawn from the sensor panel. Thresholds are used to avoid false detection of approaching objects.

Abstract: A method and apparatus for determining when an approaching object has contacted a sensor panel. The method includes the steps of (a) using a controller which is connected to the sensor panel, (b) determining a value for the approaching object based on a current flow between the sensor panel and the controller, (c) repeating step (b) until the value has reached a maximum value, and (d) generating a signal when the value has reached the maximum value to indicate that the object is contacting the sensor panel.