A 0.4 V driving multi-touch capacitive sensor with the driving signal frequency set to (n+0.5) times the inverse of the LCD VCOM noise period

The time-periodic property of the LCD VCOM noise is utilized to reduce the effect of the VCOM noise on the mutual-capacitance measuring touch sensor placed on a LCD panel. The amplitude of the touch sensor driving signal (VSTM) can be reduced reliably down to 0.4 V with the reporting rate of 189 Hz, by using the following two methods. (1) The frequency of VSTM is set to (n+0.5)·f
_N
, by synchronizing VSTM to a LCD gate driver signal with a referenceless CDR. fN is the inverse of the LCD VCOM noise period (TN) and n is a positive integer. (2) The reset period of the RX integrator is set to 2·TN.