How to suppress resistive touch interference in HMI (Human Machine Interface) systems?

To suppress interference from HMI resistive touchscreens, it's necessary to address their analog voltage measurement operating principle. Resistive touchscreens locate themselves by detecting voltage values in the X and Y directions, making them highly susceptible to power supply noise and electromagnetic interference. First, provide an extremely clean analog power supply to the touchscreen controller. It's recommended to use a dedicated LDO power supply with LC filters before and after it, such as using PBZ1608 ferrite beads and 10μF MLCC capacitors. The touchscreen's X+, X-, Y+, and Y- leads are sensitive high-impedance analog lines and must be wired with shielded twisted-pair cables or shielded FPCs, with the shield grounded at one end. On the PCB, these four lines should be short and kept away from digital signals, and can be protected with a ground plane.

A small capacitor, such as 10nF-100nF, can be connected in parallel to the analog input pins of the controller, leading to analog ground, to absorb high-frequency noise. Software algorithms such as multiple sampling and averaging, and software filtering can effectively suppress random interference. If the touchscreen is stacked with the display screen, attention must be paid to potential coupling interference from the backlight drive and display signals; ensure that their ground lines are separated or properly handled. In industrial environments with severe interference, infrared or surface acoustic wave (SAW) touchscreens can be considered as alternatives to resistive touchscreens. By optimizing power supply, shielded wiring, and software processing, and utilizing filtering components from Echotronics, the anti-interference capability of resistive touchscreens can be effectively improved.