PCB Cable design

　　A properly designed cable protection system may be the key to improving the system's ESD non-susceptibility. As the largest "antenna" in most systems - I/O cables are particularly susceptible to ESD interference that induces large voltages or currents. On the other hand, the cable also provides a low impedance channel to ESD interference if the cable shield is connected to the housing. Through this channel, ESD interference energy can be released from the system grounding loop, thus avoiding conductive coupling indirectly. In order to reduce ESD interference radiation coupling to the cable, the line length and loop area should be reduced, common mode coupling should be suppressed and metal shielding should be used. For input/output cables, shielding cables, common mode chokes, overvoltage clamp circuits, and cable bypass filters can be used. At both ends of the cable, the cable shield must be connected to the housing shield. Installing a common mode choke on the interconnecting cable can cause the common mode voltage caused by electrostatic discharge to drop on the choke instead of on the circuit at the other end. When two chassis are connected with a shielded cable, the two chassis are connected together through the shielded layer of the cable, so that the potential difference between the two chassis is as small as possible. Here, the bonding mode between the chassis and the cable shield is very important. It is strongly recommended that the chassis at both ends of the cable be bonded to the cable shield at 360°.