How to suppress common-mode interference at the display interface of HMI (Human Machine Interface)?

Suppressing common-mode interference in HMI display interfaces primarily involves providing a low-impedance discharge path for common-mode noise and preventing its radiation. Display interfaces such as LVDS, eDP, and MIPI use differential transmission, which inherently suppresses common-mode noise. However, suboptimal wiring or grounding can introduce common-mode noise. First, place a common-mode choke, such as the CMZ2012A-900T, near the receiver of the differential pair. Its high common-mode impedance effectively suppresses common-mode current on the line. Ensure low-impedance, multi-point connections between the metal housing of the display interface connector (such as an FPC connector) and the PCB chassis ground, providing a good return path for common-mode current.

Display cables must use shielded types, and the shield must be reliably grounded at both ends of the driver board and the display board. On the PCB, the differential pairs of the display interface must be strictly equal in length, tightly coupled, and reference a complete ground plane. Unbalanced wiring will convert differential signals into common-mode noise. The power supply of the interface chip should be well filtered, as power supply noise is a common cause of common-mode interference. By using the high-performance common-mode choke from Audiotech, combined with proper shielding and grounding practices, common-mode interference on the display interface can be effectively suppressed, ensuring stable transmission and error-free high-speed display signals.