Many customers ask us if whether Signal & Power Integrity analysis can offer a solution for EMC problems. In order to answer this question, we asked Melvin Mengerink, Signal & Power Engineer at Sintecs, to explain wat EMC is and how it relates to SI & PI.
What is EMC?
ElectroMagnetic Compatibility is about a system being able to function correctly in an electromagnetic environment as well as quantifying its own radiation towards this same environment. EMC can be divided into two categories, EMR and EMI.
EMP and ESD are not included in this division.
- EMR: Electro Magnetic Radiation is the radiation that your system sends into the environment. This radiation can have a negative effect on nearby system that can cause system failure.
- EMI: Electro Magnetic Immunity is the susceptibility of your system in an electromagnetic environment created by nearby systems. These electromagnetic fields can also negatively affect the system causing system failures if threshold margins are slim or high-speed designs are used.
How does it relate to SI?
The creation of fringe fields is because a potential difference (E-field) is created. Due to this potential difference a current will start flowing, which will generate a magnetic field (B-field). If the signal integrity is of good quality the signal change will be limited to the edge transition. If reflections occur, due to impedance discontinuities, the signal can start to ring. This ringing will create a longer and more frequent change in signal potential, thus causing more EMR. Ringing or overshoot can also cause more crosstalk, inter-symbol interference or less threshold margin.
How does it relate to PI?
Power distribution networks (PDN’s) can also create EMR effects or be susceptible to EMI-problems. The name switching power supply already speaks for itself, but not only the switching behaviour has effect on the PDN power integrity. The PDN’s are used to create threshold levels for the digital logic circuitry. If the PDN is noisy or shows rail collapse and ground bounce issues the signals may be latched in unreliably. Variations and voltage fluctuations in a PDN can be the result of EMC (Transmitted) or EMI (Received) problems. To counter these effects proper decoupling and filtering must be used. PCB routing has a significant effect on EMC, EMI and power integrity response in general.