SMD Pulse Transformer
In order to convey pulsed signals at high speeds over Ethernet links, stable galvanic isolation must be provided between the input and output. The new TDK ALT4532 series of SMD pulse transformers employs an innovative automated coil winding technique and features very uniform electrical properties with a much smaller footprint.
LAN connectivity is becoming a standard feature not only in PCs, but also in digital devices ranging from digital TVs to multimedia appliances. Conventional pulse transformers for LAN applications consist of a toroidal (ring-shaped) core, on which the primary and secondary coils are wound. Toroidal transformers exhibit lower leakage flux and are able to deliver better performance than other transformers with cores that inherently have an air gap. For this reason, pulse transformers have traditionally been designed as toroidal transformers. Due to their shape, however, the coils are normally hand-wound because automated winding is difficult to implement, which unavoidably results in tolerances between finished units and presents an obstacle to stable quality and mass production.
Despite their rather simple operating principle and fundamental design, pulse transformers are actually quite difficult electronic components to build well. Aspects such as design, choice of core material, and winding method affect the outcome considerably, and uniform electrical characteristics are not easy to achieve in mass production. The TDK ALT series of SMD pulse transformers employs a new design that enables a manufacturing process with automated winding.
The design of the new SMD pulse transformers is based on that of the latest TDK SMD common-mode filters, which are used extensively as noise suppression components. A common-mode filter is similar to a pulse transformer in that it also employs two windings. TDK-EPC’s pioneering approach uses automated winding on a rectangular drum core and then joins it with a flat plate core (Figure 1). The new SMD pulse transformers are the first in the industry to be manufactured with automated winding.