Low-Power Touch-Sensing Circuit With Reduced Scanning Algorithm for Touch Screen Panels on Mobile Devices

Touch screen panel (TSP) technology has dramatically enhanced the connectivity between man and machine, in particular within mobile consumer electronics where mobility is a key design criterion. This paper introduces a novel charge-sensing technique derived from the behavioral characteristics of a mutual capacitive touch screen panel. The approach is based on a reduced scan algorithm whereby both the target and its surroundings form the node and the selection process is conducted in two phases. In the first phase, the introduction of a charge on the TSP is sensed, while the second phase evaluates when the touch event occurs on the TSP. The proposed algorithm reduces the number of sensing nodes activated during the waiting period by observing the behavior of a single row within the charge sensing array, as opposed to the more conventional approach in which all TSP nodes are scanned. As a result, power consumption is reduced by 60% during the sensing phase, while the dynamic sensing range is increased by a factor of 38% for a complete two-stage sensing cycle.

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