New-Tech Europe Magazine | Jan 2018

whose interaction can only be tested after finalizing the layout) and improved procurement security, because standard footprints have established themselves in the market for these converters from 1 to 3W, which are available from different vendors. Interface Module as an All- in-One Solution As another design simplification enabling hardware designers to focus on their core tasks, modules can combine a signal isolator and a DC/ DC converter. Manufacturers of such all-in-one modules, including Murata, can thus ensure that the components interact optimally and that integration is advanced more and more. Users therefore have a very straightforward option to implement an isolated interface reliably, quickly and at very low component count. Cost is often cited as a disadvantage of modules and especially of all-in-one solutions. It is true that the purchase price of a module is higher than the sum of individual components. However, it is often overlooked that modules entail almost no additional costs for development, testing and any applicable safety certifications. In addition, procurement and inventory are much easier. Considering all aspects, selecting an all-in-one module may be the better alternative especially for applications manufactured in volumes of less than tens or hundreds of thousands annually. Design Simplifications Enabled by Additional Functions This applies even more if the all-in-one solution provides additional functions enabling cost reductions in other parts of the system design. As a good example, Murata’s NM485 interface module enables the implementation of an isolated interface according to the RS-422 or

Figure 1: 78253 standard transformer series from Murata

driver logic, filters and a transformer providing galvanic isolation. Significant board area may be required because of the discrete implementation, which can be an important consideration if space is at a premium. As an example, Figure 1 illustrates a galvanically isolating transformer that is listed in the reference design of an interface IC manufacturer and is available as a standard component from Murata.

As another widespread alternative, ready-made, isolated DC/DC converter modules are available in different packages, for different isolation voltages and for the most common combinations of input and output voltages. Advantages of these turnkey modules include reduced development overhead (by using a pre-tested and pre-characterized component instead of at least a handful of components

Figure 2: NM485 All-in-One solution for an RS-485 interface with additional remote supply voltage

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