Agilent 5991-4167EN Physical Layer Testing of the USB 2.0 Serial Bus - Application Note c20141006 [10] free download

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Keysight Technologies Physical Layer Testing of the USB 2.0 Serial Bus Using InfiniiVision 6000 X-Series and Infiniium Series Oscilloscopes Application Note Introduction The Universal Serial Bus was developed and standardized by a group of leading companies from the computer and electronics industries in 1995. These companies also formed the USB Implementers Forum, Inc. (USB-IF) as a non-profit corporation to publish the specifications and provide a support organization and forum for the advancement and adoption of USB technology. USB 2.0 Overview USB 2.0, which includes high-speed (480 Mbps), full-speed (12 Mbps) and low-speed(1.5 Mbps), is used today in a broad range of computers as well as embedded designs. One example of an embedded design is the automotive charging and sync USB port available in a variety of newer vehicles. Beyond traditional PC computers, most other types of electronic products, such as medical equipment or industrial control systems, include USB interfaces as well. With almost 20 years of functional interoperability experience behind it, any new products shipped must meet the user's expectations that it will just work. This is why testing and debugging USB designs using high-speed, full-speed or low-speed USB 2.0 interfaces is critical to ensure reliability of operation and meet end user expectations. To complement the USB specification in real products, the USB-IF maintains a compliance program that provides reasonable measures of acceptability. Products that pass compliance testing have the right to license the USB-IF certified USB Logo. One of the key components of USB compliance testing is physical layer testing. This has helped USB product success and acceptance by creating a very stable and interoperable ecosystem. Since that time USB has become ubiquitous. Over 10 billion USB products have shipped since its introduction and it has effectively replaced all other external IO interfaces. There are an estimated 4 billion USB products shipped annually 3/4 of them (3 billion) are using USB 2.0. USB-IF physical layer compliance certification is typically required by computer OEMs for suppliers of USB devices and silicon chip-sets. However, full compliance certification testing is typically not a requirement for embedded products. Nonetheless, R&D testing and verification of physical layer characteristics of embedded designs with integrated USB interfaces is extremely important to ensure reliable operation of end-products. Simply selecting USB components, integrating them into an embedded design, and then hoping that everything functions is not good enough. Even if the system appears to function, how much margin does it have? Or how does it perform under various environmental conditions such as temperature or humidity? This application note begins wit