Tektronix - Everyday Design and Debug with an MDO3000 Series Oscilloscope

Our thanks to Tektronix for allowing us to reprint the following article.

 

1. Finding an Anomaly in a Signal

 

Discovering and capturing signal anomalies can be one of the most difficult challenges in the debug process. Subtle or infrequent anomalies on just one signal can mean the difference between a design that works reliably and one that does not.


In this section, an MDO3000 with FastAcq, advanced triggering, and automated search is used to discover, capture, and characterize an infrequent event in a digital signal.

 

In this example, while probing signals on the circuit board, faint traces are occasionally visible on this waveform, indicating infrequent and unexpected events that do not look like the digital signals.

 

The faint traces in the intensity-graded display in Figure 2 indicate infrequent anomalies exist on the signal, but they disappear from the display too quickly to measure. Although infinite persistence could help when looking at a single signal, it is not compatible with rapid probing across a circuit board.

 

To quickly discover signal anomalies as the user probes around the design, and to get a sense for how often the anomalies are occurring, color-graded FastAcq mode is enabled. The FastAcq acquisition mode speeds up the waveform acquisition rate to over 280,000 waveforms per second, quickly capturing and displaying any anomalies. The temperature display indicates the most frequent signals in red and the least frequent signals in blue.

In this 3.3 Volt digital signal, occasional narrow pulses or glitches are visible in Figure 3, and low-amplitude runt pulses, which are a little over 1 Volt high, also appear in a blue color...

 

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