Datasheet

Application Note
www.tektronix.com/bench6
The positive and negative pulse widths are more rigorously
checked by changing the MSO acquisition mode from Single
to Run. The positive and negative pulse statistics (mean,
minimum, maximum and standard deviation) are accumulated
across multiple acquisitions. You can select between 2 to
1,000 acquisitions for the measurement statistics.
Figure 10 measurement statistics show the positive pulse
width mean is 23.87 ns with a 53.62 ps standard deviation.
The positive pulse width minimum is 23.76 ns and the
maximum is 24.00 ns which are within the specifications.
Likewise, the negative pulse width measurements are verified
to be within the specifications. At this point, the verification of
the TTL burst signal is progressing smoothly.
This verification technique depends on which parts of the
continuous signal are being acquired and analyzed. A more
robust verification technique is to have the Tektronix MSO
Series check every pulse with its powerful triggering capabilities.
For example, the MSO can be set up to verify the TTL burst
signal by measuring each and every positive pulse and
triggering on non-conforming pulse widths smaller than 23.2
ns. The single shot acquisition mode is used to stop the MSO
after it triggers, allowing the non-conforming pulse to
be analyzed.
In Figure 11, the MSO triggered on a non-conforming positive
pulse less than 23.2 ns. Two errors are captured in this
acquisition. The first error is that the seventh pulse is 3.636 ns
wide which is smaller than the 23.2 ns minimum specification.
The second error is the missing eighth pulse. This is an
example of using the MSO digital triggering to look for non-
conforming digital signals. Also, in looking for non-conforming
digital signals, the MSO trigger can be used to look for pulses
greater than 25.6 ns. In this case, no problems were found.
The root cause of this error is a design flaw. The signal that
controlled the gating of the pulses was asynchronous to the
generation of the pulses and it occasionally varied in its gating
duration. As a result, the internal gating signal intermittently
chopped off the last pulse and clipped the seventh pulse.
This verification technique of triggering on errors can be used
to monitor the signal for long durations, such as overnight or
over the weekend, to provide even more rigorous verification
of the design.
Figure 10. MSO Series measurement statistics verifying TTL burst signal positive and
negative pulse width.
Figure 11. MSO triggered on positive pulse width error of 3.636 ns.