How to implement interference-resistant wiring for touch signal lines in HMI (Human Machine Interface) systems?

Improving the anti-interference routing capability of HMI touch signal lines requires addressing shielding, balancing, and filtering. For analog signal lines of resistive touchscreens or drive sensing lines of capacitive touchscreens, these signals are very weak and susceptible to interference. First, in PCB layout, touch signal lines should be as short as possible and kept away from noise sources such as clock lines, power lines, and backlight drive lines. Differential routing is preferred; even if the original signal is single-ended, it can be routed parallel to a ground line to form a pseudo-differential pair, with strict control over line spacing and length matching. For external touchscreen cables, flexible circuit boards or cables with shielding layers must be used, and the shielding layer must be reliably grounded at both ends (or at one end according to the grounding strategy).

Near the signal input pins of the touch controller chip, small capacitors, such as 10pF-100pF, can be connected in parallel to analog ground to filter out high-frequency noise. Connecting a small filter resistor, such as 100Ω, in series on the signal lines also helps suppress high-frequency interference. Placing touch signal lines on inner layers and wrapping them with ground planes on both sides provides excellent shielding. ESD protection devices from Eintech, such as the ESD5V0D3B, can be connected in parallel to the touch signal line to absorb electrostatic pulses from the human body or surrounding environment, preventing chip damage. By comprehensively utilizing these wiring techniques and protective measures, the robustness of the touch signal in complex electromagnetic environments can be significantly enhanced.