Connect-Tek USB-2 Manuel d'utilisateur télécharger pdf (Page 3)

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Understanding and Performing USB 2.0 Physical Layer Testing and Debugging

While performing compliance testing, you need to set up the

worst-case USB 2.0 topology scenario to ensure a sufﬁcient

test margin. Devices are tested in the 6th tier to ensure the

worst-case scenario. Further, each hub level is referred to as

a tier. The hub-under-test (HUT) is plugged into the 5th tier so

that it operates on the 6th tier.

Test Equipment

Signal quality testing requires a real-time oscilloscope with a

bandwidth of 2 GHz or higher, such as the MSO/DPO5204,

DPO7254 or DPO7354, for high speed USB signals, and an

oscilloscope with a bandwidth of 350 MHz or higher, such as

any of the MSO/DPO5000 or DPO7000 Series, for low and full

speed USB signals. Single-ended probes like the TAP1500,

TAP2500, TAP3500, and P6245

are needed for low and full

speed USB testing. Differential probes such as the TDP1500,

TDP3500, and P6248

are required for high speed USB

testing. In addition, this testing requires test software and a

USB test ﬁxture.

Figure 1 shows the operation of the TDSUSB2 (option USB)

compliance test package and the TDSUSBF test ﬁxture on a

DPO7254. This test package fully automates the signal quality

test process, allowing designers to perform quick and easy

tests on their designs.

A user must select the measurements to be performed for a

particular signal speed (low, full or high speed). The application

must then be conﬁgured based on tier (tier to which the DUT

is connected), test point (test point of the DUT — near or far

end), and direction of trafﬁc (upstream or downstream testing),

as shown in Figure 2. After completing these two steps, the

user then runs the application.

The test package eliminates the task of manual, time-

consuming oscilloscope set-ups, cursor placements and

comparison of test results with USB 2.0 speciﬁcations. The

results are automatically displayed as a results summary and

details, as illustrated in Figure 3.

Figure 1. TDSUSB2 compliance test package running on a DPO7254. Figure 2. TDSUSB2 compliance test package running on a DPO7254.

Figure 3. Measurement results are automatically displayed using the TDSUSB2

compliance test package.

Requires a TPA-BNC adapter when used on an MSO/DPO5000 or DPO7000 Series model.

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Connect-Tek USB-2 Manuel d'utilisateur Page 3

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