A SNR-Enhanced Mutual-Capacitive Touch-Sensor ROIC Using an Averaging With Three Specific TX Frequencies, a Noise Memory, and a Compact Delay Compensation Circuit

Abstract

To enhance the signal-to-noise ratio of a mutualcapacitive touch-sensor, three methods are used to implement read-out integrated circuit ( ROIC); an averaging method with three specific transmitter frequencies of ( n + 0.5) times the frequency of a gate driving signal ( GCLK) of LCD with an integer n, a noise memory method that eliminates the dc and low frequency noise by subtracting the noise data from the measured data, and a compact delay compensation method. A digital dual-loop phase-locked-loop generates the three specific frequencies automatically from GCLK. The proposed ROIC applied to a 14x16 touch-sensor panel on a 7.9-in LCD achieves the SNR of 52.9 dB with the frame rate of 367 Hz. The ROIC chip with a 0.35-mu m CMOS process takes an area of 5.64 mm(2) and consumes power of 29.7 mW.