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PCB design guidelines for ESD
Last Updated : 2011/5/5

In PCB design, the use of transient voltage rejection device (TVS) diode to suppress ESD discharge due to the direct charge injection, the PCB design is more important is to overcome the electromagnetic interference generated by the discharge current (EMI) electromagnetic field effects. This article will provide ESD protection can be optimized PCB design guidelines.

Circuit loop
Current into the circuit through the induction loop, the loop is closed, and with changes in magnetic flux. Current amplitude proportional to the area with the ring. Larger loop contains more flux, which induces in the circuit a strong current. Therefore, we must reduce the loop area.

The most common loop shown in Figure 1, formed by the power and ground. Possible conditions, can be used with multiple power and ground layer PCB design. Multi-layer circuit board not only between the power and ground to minimize loop area, but also reduces the ESD pulse electromagnetic fields generated by high-frequency EMI.

If you can not use multi-layer circuit board, then for power and ground wire must be connected into the grid as shown in Figure 2. Grid connection can play the role of power and ground planes, vias connecting layers of printed lines in each direction through hole connections within the interval should be 6 cm. In addition, the wiring, the power and ground traces as close as possible can reduce the loop area.

Reduce the loop area and the induced current is to reduce the interconnection of another parallel path between devices.

Must be longer than 30 cm when the signal cable, can protect the line in Figure 5. A better approach is to be placed in the ground near the signal line. Signal line should be from the protection line or ground layer 13 mm or less.

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