Review: Trilogy of Magnetics (5th Edition)

Article By : Kenneth Wyatt

The fifth edition from Würth Elektronik adds hundreds of pages of reference material. It's worth the upgrade.

Trilogy of Magnetics,
by Würth Elektronik,
now in its 5th edition.

Würth Elektronik eiSos (WE) continues to sell a monster 4-pound, 826-page reference book, the Trilogy of Magnetics, now in its 5th edition. The last time I reviewed the 4th edition was September 2012 (Ref. 1). So, let’s see what the differences are from seven years ago.

The cost for this latest edition is the same €49 or $49.99 USD, orderable through the WE web site or your local sales rep (Ref. 2). The hardbound book has been greatly expanded and organized into three main sections: basic principles, components and applications. While there are lists of specific part numbers, most of the book is devoted to theory and practical applications.

The first section, Basic Principles, is expanded by over 100 pages to 261 and includes new sections on filter and transformer basics, switch mode power supply basics, wireless power transfer and RF design basics. It also covers the foundations of inductive and ferrite components and includes equivalent circuit diagrams and simulation models.

The components section (201 pages) introduces inductive and ferrite components, their properties and best applications. Included are EMC components and inductors, transformers, wireless power transfer, signal & communication, RF components, circuit protection components, and “low temperature co-fired ceramic” (LTCC) devices, such as filters and wireless antennas.

The applications section (313 pages) offers comprehensive applications information on filter circuits, audio, video, I/O interfaces, motor control, switch mode power supplies, mains filters, wide band-gap devices, wireless power transfer and RF applications. There are numerous industrial and consumer applications pulled from real-world designs. Numerous design tips are sprinkled throughout the text.

Some of the questions the book’s answers include:

  • How are we supposed to understand the information about inductors and ferrites that is given in data sheets?
  • What effect does the ferrite core material have?
  • What do core losses and saturation mean in my application?
  • How do you design SMPS transformers?
  • How can I take EMC into account right when I begin my design?
  • How should I design my circuit board layout?

HDMI ports have always been a problem for EMI compliance. Properly laying out the HDMI section is important to low-EMI performance. In addition, proper specification of HDMI cables is vital, as many have poor termination from the shield-to-connector shell. See my three-part article on proper PC board layout for low EMI (Ref. 3). Figure 1 shows an example PCB layout for minimizing EMI.

As wireless technology has matured, there has been more reliance on low-temperature co-fired ceramic (LTCC) devices, such as low pass and band pass filters and wireless antennas. Figure 2 shows the manufacturing process for these devices, where components and traces are laid out in layers and then the whole set of ceramic layers is collated and fired to produce the part.

LTCC manufacturing processFigure 2. Low-temperature co-fired ceramic (LTCC) manufacturing process.Image courtesy of Würth Elektronik.

These LTCC devices may be found in the latest cellular phones and other wireless products. Figure 3 shows how two LTCC antennas are connected through an impedance matching circuit to a typical wireless IC.

LTCC manufacturing processFigure 3. An example of a LTCC application for wireless antennas. Image courtesy of Würth Elektronik.

Other applications include everything from small-signal and mains filters to audio and video circuits to interfaces, RF and power supply circuits.

There is no longer a CD included with the book, but the design application software is readily available from the WE web site and is regularly updated. Their free design programs include REDEXPERT (real-time simulation and calculation of losses), Analog IC Selector (manufacturer independent selection), Monolithic Power System DC/DC Designer, and included is Texas Instruments’ WEBENCH. WE design software may be downloaded from their web site under the “Toolbox” tab (Ref. 4).

There are multiple applications using Linear Technology’s LTspice, which is available from the Linear web site (Ref. 5).

The book focuses on selecting components, circuitry and layout recommendations, and takes EMC perspectives into account. There is also a dictionary of terms in the appendices.

I own a number of good reference books on EMC and this one deserves a space on your bookshelf. Highly recommended.

Kenneth Wyatt is president and principal consultant of Wyatt Technical Services.

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