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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 with a discussion of measurement requirements for the USB 2.0 serial
bus. We then discuss how both the Keysight Technologies, Inc. 6000 X-Series and Infiniium Series
oscilloscopes address these challenges and which scope is the best choice for the type of testing and
test coverage the product developer needs to perform.
03 | Keysight | Physical Layer Testing of the USB 2.0 Serial Bus Using InfiniiVision 6000 X-Series and Infiniium Series Oscilloscopes