E2667B Datasheet, PDF (4/10 Pages) Keysight Technologies – USB 2.0 Signal Quality Test Option

04 | Keysight | DSOX4USBSQ and DSOX6USBSQ USB 2.0 Signal Quality Test Option for 4000 and 6000 X-Series - Data Sheet
Probing the USB 2.0 Differential Bus
To test USB 2.0 low- and full-speed designs, the only probes required are two 10:1 passive
probes, which are shipped as standard accessories with every Keysight InfiniiVision X-Series
oscilloscope.
To test USB 2.0 hi-speed designs based on pre-compliance standards with the appropriate
device or host test fixture, 50-Ω SMA cables with SMA-to-BNC adapters are all that is required.
For this use-model of testing, the test fixture is programmed to generate a specific test pattern.
However, during the design and debug phase of product development, engineers often need to
test “live traffic” in their hi-speed designs (non-compliance testing). In this case, a test fixture
is not required, but a differential active probe with sufficient bandwidth is required. For this
use-model of testing, Keysight recommends an InfiniiMode N2750A Series differential active
probe shown in Figure 3.
The N2750A Series probe is more than just a differential probe. With the press of the
InfiniiMode button on the probe, you can quickly toggle between viewing the differential signal,
high-side (D+) relative to ground, low-side (D-) relative to ground, or the common-mode
signal. Although ultimately it is the quality of the differential signal that really matters, if signal
integrity issues do exist on the differential bus, they can often be caused by issues such as
system noise coupling into just one side of the bus (or perhaps improper PC board layout and
termination related to just one side of the bus).
Figure 3. Keysight’s InfiniiMode N2750A Series differential active probe.