Modelling of PCB variations and its impact on microcontroller immunity

Abstract

Within any electronic product lies a printed circuit board (PCB). This PCB is used to provide a convenient method of holding the electronic circuit in place, while connections are made between these components. The PCB can then be placed into harsh environments such as car engine bays. What influence does the PCB have on the EMC performance of the microcontroller circuit? It is important to understand this influence and determine ways how it can be exploited to improve the circuit immunity. In order to understand how the PCB contributes to the immunity performance of a microcontroller based electronic circuit, simulations of two and four layer PCBs were performed. From simulation, it is seen that the PCB is not an inert object, but has properties that affect immunity performance. Methods to improve the immunity performance of microcontroller based circuits are suggested. EMC immunity of the microcontroller based circuits can be affected by not only the layout and layering of the PCB, but also by the dielectric constant of the materials used. This implies that the design process for modern digital circuits should not only optimise the layout of the PCB, but take account of materials used in the PCB construction. Both of these should be treated as important design parameters, and any changes carefully weighed.