How to minimize the grounding impedance of I/O modules

Minimizing the grounding impedance of I/O modules is fundamental to reducing ground noise voltage and improving immunity. First, use a large copper area as the ground plane, and ideally, use a multilayer board to place the ground plane on a complete inner layer. Increase the number and density of grounding vias, especially around chip ground pins, filter capacitor ground terminals, and connector ground pins; vias should be filled with drilled holes and copper plating. The connection point between the ground plane and the chassis ground should use multiple parallel screws or metal supports, and conductive paste should be applied to reduce contact resistance.

Ground traces on the PCB should be short and wide, avoiding the use of thin, long traces. For high-current loops, the ground trace width needs to be calculated based on the current magnitude; typically, 1mm width carries 1A of current. At the system level, ensure that the ground bus or ground bar has sufficient cross-sectional area and that the connecting bolts are securely tightened. The DC resistance of the ground path can be accurately measured using a four-wire Kelvin method, while a network analyzer can measure the grounding impedance at high frequencies. The design goal is to ensure that the impedance from any point in the circuit to the reference ground point is sufficiently low within the frequency range of interest.