A Low Power Self-capacitive Touch Sensing Analog Front End with Sparse Multi-touch Detection

Capacitive sensing technology is ubiquitous in today's electronic devices. This paper proposes a novel architecture for the design of an ultra low power self-capacitive touch sensing analog front end (AFE) by exploiting the sparsity of simultaneous touches with respect to the number of sensor nodes. It is possible to significantly reduce the complexity and the power consumption of the AFE by migrating the computational burden to the digital processor which usually have surplus computational power. Based on the 1-bit compressive sensing theory, the ADC(s) in the AFE can be replaced by a single comparator. The number of measurements required in order to resolve the touch positions is related to the number of simultaneous touches rather than the number of sensor nodes. Detailed AFE architecture and the capacitance measurement process will be presented along with a corresponding digital reconstruction algorithm run by the digital processor.