PCB layout is a key element of ESD protection , rational PCB design can reduce unnecessary troubleshooting and rework costs arising . PCB design , the use of transient voltage suppressing device (TVS) diodes to suppress the direct discharge of the charge injection due to ESD , so the PCB design is more important to overcome the discharge current generated by the electromagnetic interference (EMI) electromagnetic field effect . This article will provide ESD protection can be optimized PCB design guidelines.
Circuit loop
Sensing the current through the circuit into the loop , the loop is closed and has a changing magnetic flux . Current amplitude proportional to the area with the ring. Larger loop contains more magnetic flux induced in the circuit so that a strong current. Therefore, we must reduce the loop area .
The most common is formed by the loop power supply and ground . Where possible conditions, multi-layer PCB design with the power and ground layers. The multilayer circuit board not only between the power and ground loop area is minimized , but also reduces the ESD pulse is generated electromagnetic field of high frequency EMI .
If you can not multi-layer circuit board , then the line is used for power and ground must be connected to a grid . Grid connection can play the role of power and ground planes , used to connect layers hole traces , vias connecting the interval in each direction should be within 6 cm . Further , in the wiring , power and ground traces to be as close as possible to reduce the loop area .
Another way to reduce the loop area and the induced current is reduced interconnection between devices in parallel paths .
When must be longer than 30 cm signal cable can be used to protect the line . A better approach is to be placed near the signal line formation . Signal lines should protect the wire from ground level or less than 13 mm .
The length of each sensor signal line ( 30 cm ) or its power cord ground wire cross layout. Cross- connection rules from top to bottom or left to right must be spaced .
Circuit wiring length
Long signal lines can also become ESD pulse energy receiving antenna , try using a shorter signal lines can reduce the signal line ESD electromagnetic field as a receiver antenna efficiency.
Try to interconnect devices in adjacent positions , in order to reduce the length of the printed line interconnection .
To charge injection
ESD discharge directly to the ground plane may damage sensitive circuitry. Using TVS diodes while also using one or more high-frequency bypass capacitor , the capacitor element is disposed between the power and ground wearing . Bypass capacitor reduces the charge injection , maintaining the voltage difference of the power and ground port .
