针对采用触摸预测和窗口采样(TPWS)稀疏读出策略实现的电容触摸屏系统容易受到显示噪声和充电器噪声干扰的问题,本文提出了并行互补驱动和差分感应的方法以提高系统的信噪比.基于本文提出的并行驱动和差分感应方法,并结合 TPWS 系统的特点,采用0．35μm CMOS 工艺设计实现了一个48通道电容触摸屏模拟前端 IC,并设计了一个11．6 in 原型触摸屏系统用于评估该 IC 的性能.测试结果表明,本文设计的 IC 不仅能满足 TPWS 系统对于点测量和线测量的功能需求,并且系统的信噪比从原来的25．0 dB 提升到了35．8 dB.
Capacitive multi-touch screens using touch predicting and window sensing (TPWS)readout strategy are susceptible to display noise and charger noise interferences.In this paper,a parallel com-plementary driving and differential sensing method are proposed to improve the SNR of TPWS system.A new 48-channel analog front-end IC is designed and realized using 0.35 μm CMOS process based on the parallel complementary driving and differential sensing method.In addition,an 1 1.6 in prototype touch screen system is designed to evaluate the performances of the analog front-end IC. The measurement results indicate that,the analog front-end IC designed in this paper can satisfies the requirements of TPWS system for line and point scanning,and furthermore,the SNR of the TPWS system is increased from 25.0 dB to 35.8 dB.
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