Connect-Tek USB-2 Manual do Utilizador descarregar pdf (Página 11)

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Understanding and Performing USB 2.0 Physical Layer Testing and Debugging

Test Fixture

The test ﬁxture is the most crucial component that enables

probing for every test set-up. The ideal test ﬁxture should

provide access to the differential data lines (D+, D-) and V

BUS

and offer access/connections via on-board USB connectors

or wired dongles.

For receiver sensitivity testing, SMA cables are needed to

connect the data generator to data lines to stimulate the

device. Cable access is also needed to allow impedance

measurements by a TDR measurement device.

The TDSUSBF is a comprehensive compliance test ﬁxture to

enable USB 2.0 testing, as shown in Figure 12.

Test Software

A user may choose among fully automatic test software, semi-

automated test software and manual testing.

Fully Automatic Test Software

Fully automatic test software, such as the option USB

compliance test package, substantially improves test efﬁciency

by providing automatic oscilloscope set-ups, automated

highspeed tests and quick “one-touch” testing. This test

package drastically reduces the test time and chances of any

erroneous measurements.

Semi-Automated Test Software

As the name implies, this kind of solution automates certain

tests but invariably omits certain requirements of compliance

testing, resulting in reduced overall throughput. Examples

of some tests that still need to be manually performed are

high-speed compliance tests such as receiver sensitivity,

CHIRP and monotonicity tests, as well as rise and fall time

calculations.

Manual Testing

The complexity of the tests and setups demand a high level of

expertise from the test engineer. Setting up the oscilloscope

can be a tedious and time consuming task, as oscilloscope

set-ups differ for various test conﬁgurations. A user is

compelled to make continuous references to exhaustive

documentation about test procedures, making testing difﬁcult

and signiﬁcantly reducing efﬁciency.

Probes

Probes are a critical component of the measurement system

to perform various USB 2.0 compliance tests. Tektronix

offers differential (P6248

, TDP1500, TDP3500), single-

ended (P6245

, TAP1500, TAP2500, TAP3500) and current

(TCP202

, TCP0030) probes that allow access to high-density

boards with ﬁne-pitch, hard-to-reach components while

maintaining maximum signal ﬁdelity.

Figure 12. TDSUSBF Test ﬁxture.

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

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