Applied Embedded Electronics

Chapter 6. Electromagnetic Interference and Electrostatic Discharge

Electromagnetic interference (EMI) deals with unwanted signal coupling and other secondary effects within or between electronic systems. The terms electromagnetic compatibility (EMC) and signal integrity are often used as generalized terms to cover most of these topics. EMI and radio frequency interference (RFI) are often used interchangeably, and herein are considered the same thing. Historically, RFI has been in use since the early era of analog radios. In this book, the terms EMI, RFI, crosstalk, and noise are used interchangeably.

Electrostatic discharge (ESD) is included in this chapter as a special topic under the umbrella of “unwanted” signals. Many circuits discussed here affect both EMI and ESD performance.

Any digital electronic system creates EMI, with the noise magnitude determined by the clocking rates, number of gates, and presence of any other actively switching devices. Designers should recognize that the environment is awash in electronic noise due to active electronics, radio devices, solar noise, grid power systems, and countless others. Designers need to limit the magnitude of the EMI created by their products, and protect their electronics from the noise of the outside environment.

Within an electronic system, internal noise generated can also be a detriment inside the same system. Sometimes internal noise can reduce accuracy, degrade performance, or make a device nonfunctional.

ESD events ...