A 6.9mW 120fps 28×50 capacitive touch sensor for 1mm-ϕ stylus using current-driven ΔΣ ADCs

This paper presents a 6.9mW 120fps 28×50 channels capacitive touch sensor for 1mm-ϕ stylus. A current conveyor analog front-end enables a current signaling before its voltage conversion. A current-driven ΔΣ ADC directly interfaces to the differential current for the digital conversion. A test IC is fabricated in 0.18μm CMOS process. This work achieves SNR of 41.7dB with 1mm-ϕ stylus, consuming only 6.9mW. This results in an energy efficiency of 0.41nJ/step which is more than 4×improvement on the state-of-the-art works.