Oscillator-based Touch Sensor for Mobile Applications
In this thesis, an oscillator-based touch sensor system is presented. Existing technologies for touchscreen sensors include resistive, capacitive, infrared, and optical imaging; however, none of them is suited for remote sensing in mobile applications. The goal of this thesis is to explore the implementation of a remote sensor system targeted for mobile applications.
The proposed design uses an input-loaded oscillator that senses the ambient capacitance. The variation in ambient capacitance alters the operating frequency of the oscillator. A digital processing unit analyzes the change in frequency, and makes detection based on certain threshold.
The design is achieved by 65nm technology, having a core area of 335um x 230um, power consumption of 2.5mW, and runs on a clock frequency of 16MHz. The system's sensitivity is one order of magnitude higher than current touchscreen technologies, requiring a minimum ambient capacitance variation of 50fF.