Design

The development of “digital common-mode noise” within circuit devices and subsequently within circuit boards is initially formed by peak over-shoot and under-shoot currents in the power and return planes. The peak currents are attributable to the “cross-conduction” transitions in circuit devices, where the driver literally segments turning “on” before the pull-down drivers turn “off”.

This article is the second in our ongoing series about batteries. This installment provides an overview of lithium-ion batteries – typical properties, principal applications, and trends.

The reliability of electronic technologies (including the software and firmware that runs on them) can become critical when the consequences of errors, malfunctions, or other types of failure include significant financial loss, mission loss, or harm to people or property (i.e. functional safety).

The board stackup is probably the most essential piece for ensuring a successful PCB design. Modern high-speed busses require controlled-impedance traces, and whether you are using a simulation tool, a simple calculator, or the back of a napkin, you need to understand your manufacturing process to correlate your impedance calculations. This ensures that your trace widths and dielectric heights match what will actually be manufactured, and eliminates last-minute design changes.

An equivalent dipole model is proposed in this paper to represent the source of radiated electromagnetic emissions from an integrated circuit (IC). The height of an IC is usually much smaller than its length and width, so only three dipole moments are sufficient to characterize an IC in terms of its electromagnetic emissions. The dipole moments can be extracted from three TEM cell measurements. The radiated fields from the IC can then be calculated based on the extracted dipole sources. This IC emission model with three dipole moments is validated using the far-field measurements in a semi anechoic chamber for a test IC. For complex structures, it is desirable that the extracted dipole moments can be incorporated into a commercial full-wave tool as equivalent sources to simulate the radiations from an IC. This is demonstrated using an approach developed in this article.

The use of exclusion zones to keep wireless transmission devices (WTDs) (e.g., radio walkie-talkies, cellular phones, etc) from being too close to instrumentation and control (I&C) equipment and system cabinets containing this equipment remains a primary concern in existing and advanced (future) nuclear power plants. In Part 1 of this article, a background and history of how exclusion zones were developed and implemented in these plants was presented along with their advantages and limitations. In Part 2, presented here, the elements of the exclusion zone strategy are discussed followed by the demonstration of a concept often used in studying the electromagnetic compatibility (EMC) immunity of modern electronic systems. This concept—called layered immunity—is key to understanding the parts of a system where EMC system immunity must be applied. The initial thought that readers must accept before proceeding to read and understand this concept described in this article is that system immunity involves other parts of the system besides just the immunity of the individual piece of equipment requiring protection.

An experimental validation of an electromagnetic band-gap (EBG) based common mode filter is given in this article. The proposed layout technique is based on planar EBG structures altered by removing the connecting bridges between adjacent patches. The patches are properly dimensioned for ensuring the presence of frequency notches at the frequencies that should be filtered in the common-mode transfer function. The notch frequency is associated with the first resonant mode of the patch.

In our ideal world, safety, quality and performance are paramount.  However, the cost of the final component (which includes the ferrite) has in many cases, become the deciding factor. This article is written as an aide for the design engineer looking for alternative ferrite materials as a means to reduce cost.