The USB Interface from EMC Point of View


The USB [Universal Serial Bus] specification defines the mechanical and electrical characteristics, as well as the protocol layer of the interface. The cable and connector are precisely defined. USB defines two types of hardware, hubs and functions, as well as terminal devices. In theory, up to 127 devices can be linked together in a star bus topology in which the only limitation is the 7-bit address. Connections are possible between the hub and function or terminal device or between hub and hub, whereby direct connections between terminal devices are not possible.


EMC without filters is no longer possible in today's circuit technology. Electronics in tight spaces, useful frequencies up into the GHz range and also consideration of the EMC standards necessitate their use. EMC is not "nice to have" or to satisfy the regulations and standards, but is a quality feature for which the user of the product has a right. Nevertheless, EMC is often an engineering challenge and a balancing act between performance and time. Würth Elektronik would like to present you with the necessary components, as well as the necessary expertise to support you in optimally designing the USB interface. We hope to have done this with the products introduced and this brief technical article and wish you every success with your next design.

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