Low power multi-channel capacitive touch sensing unit using capacitor to time conversion method

This paper presents a multi-channel capacitive touch sensing unit for SoC applications. This unit includes a simple common processing unit and switch array to detect the touch sensing input by capacitive-time(C-T) conversion method. This touch sensor ASIC is designed based on the Capacitive-Time(C-T) conversion method to have advantages of small current and chip area, and the minimum resolution of the unit is 41 fF per count with the built-in sensing oscillator, LDO regulator and I2C for no additional external components. This unit is implemented in 0.18 um CMOS process with dual supply voltage of 1.8 V and 3.3 V. The total power consumption of the unit is 60 uA and the area is 0.26 mm².