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Placing through-hole parts is among the most expensive parts of the PCB assembly operation. Eliminating them should be a task in the life of every hardware designer. LittelFuse – the name, as always, is not a typo by the OEMsecrets crew – provide the 456 family of high performance fuses which come in a handy surface-mount case.
First of all, we must mention the obvious: if you use an SMD fuse, the assembly is no longer field repairable and must be returned to a service center for repair. This might be a problem for simple systems, but – surprisingly – usually does not cause grief as systems become complex. This is caused by the situation that extremely complex SMD assemblies cannot be repaired in the field – if the part has to go back to the lab anyways, reflowing one more package is part of the game.
LittelFuse provides a total of four different sizes of SMD fuse, all of which are outlined in our figure…
…LittelFuse offers four versions of the 0456020.ER
Surface mount fuses, traditionally, have problems with activation time. LittelFuse promises that the part can stand its rated current for at least four hours, while shutting down with in a maximum of 60 seconds if 200% of the rated current flows. Sadly, the maximum allowed voltage is rather low – depending on size, between 65 and 125V AC can be disconnected. Finally, designers working with their own PCB design software should keep in mind that the parts don’t come in traditional SMD housings. You will, instead, have to make do with the layout shown in the figure.
…These layouts are best created by hand