PCB-Level EMC, part III

Switch-mode-circuits & signallines

A measurement method for the verification of new, and the analaysis of existing Power-Distribution-Networks is presented. Pitfalls which frequently lead to erroneous ripple-measurements are uncovered. Common impedance coupling is the root cause not only of many functional issues, but also of conducted and radiated emissions. Together with field coupling it is the predominant cause of X-Talk, a key factor for a successful design! The complex nature of X-Talk is detailed, including frequency-response, rules-of-thumb and appropriate measures.

Signal characteristics and their impact on EMC are explained, possible improvements of signals and signal-paths presented. A brief introduction to differential pairs helps to counter popular misunderstandings. A number of recommendations regarding layout, stackup and circuit is derived by examining the various noise sources and coupling mechanisms imminent in switch-mode circuits. Examining ESD- and Burst-phenomena, the important steps towards good immunity are presented. The understanding of frequent connector design-flaws helps with the reduction of radiated emissions.


The attendee masters Power-Integrity measurements. He is familiar with the design of SE- and differential signal lines, limiting X-Talk to acceptable levels. The latter at times also being useful to solve the conflict of contradictory requirements for immunity and emissions. EMI of switch-mode circuits is reduced by design. He is familiar with the nature of immunity-tests and knows what to look for in connectors.

Who should attend?

Engineers and technicians confronted with EMC-issues in electronic hardware design. Printed wiring layout professionals with a fair understanding of the basics of electromagnetic theory.