Connect-Tek USB-2 Manuel d'utilisateur télécharger pdf (Page 10)

Application Note

www.tektronix.com/usb10

Effect of Oscilloscope Sample Rate on

Testing

To capture information at edge speeds as fast as 500 ps,

you need at least 10 sample points on an edge. This

requirement becomes even more important when performing a

monotonicity test, mandatory for high-speed testing.

Tektronix Solutions

The following chart lists various Tektronix real-time

oscilloscopes.

Note: USB 2.0 can encounter edge rates as fast as 500 ps.

The DPO7254 digital phosphor oscilloscope is just one of the

high performance members of the Tektronix’s Windows-based

oscilloscopes. With 40 GS/s maximum real-time sample rate

and 2.5 GHz bandwidth, the four-channel DPO7254 strikes

a balance between high performance and affordability for

veriﬁcation, debug and characterization of USB 2.0 designs.

This instrument features exceptional signal acquisition

performance, operational simplicity and open connectivity

to the design environment. The DPO7254 delivers more

than 250,000 wfms/s waveform capture rate, enabled by

proprietary DPX

acquisition technology, to detect and capture

elusive events with conﬁdence and ease.

Other higher bandwidth oscilloscopes from Tektronix can

also be used within the probes, software, and accessories

mentioned here to perform USB compliance tests. Contact

your Tektronix representative to learn more about the best

instruments for your applications.

Time Domain Reﬂectometer

A time domain reﬂectometer is required for the impedance

measurement test. The DSA8200 digital sampling oscilloscope

with 80E04 TDR sampling module provides true differential

time domain reﬂectometry (TDR), making it an ideal solution

for USB 2.0 device and cable impedance measurements.

This oscilloscope and sampling module can display both the

individual positive and negative TDR waveforms of differential

line characteristics and directly measure the impedance of

each conductor or common mode voltage of the differential

line. This test system can also display the true differential

measurements of both these lines and display the impedance

in the unit of ohms, providing the user with the required

measurements to validate any USB 2.0 device.

Signal Source

A signal source is required for the receiver sensitivity test. The

Tektronix AWG5000 and AWG7000 Series are excellent signal

sources for USB receiver sensitivity tests.

Setup ﬁles to perform USB 2.0 receiver sensitivity tests for all

of these signal sources are provided by Tektronix.

Speciﬁcation DPO7254 DPO7354 DPO70404

Rise/Fall Time 160 ps 115 ps 98 ps

Sample Rate (1 ch) 40 GS/s 40 GS/s 25 GS/s

1 2 ... 5 6 7 8 9 10 11 12 13 14 15 16

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Connect-Tek USB-2 Manuel d'utilisateur Page 10

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