DESIGN VIEW is the summary of the complete DESIGN SOLUTION contributed article, which begins on Page 2.
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For decades, engineers have relied on logic analysis as their main system-validation tool. Thanks to technology advances, the digital systems they design continue to jump in speed and complexity, requiring more sophisticated analysis tools. Logic-analyzer vendors have kept pace with industry demands in terms of speed and functionality. However, in many cases, the physical connection (i.e., the probe) from the analyzer to the target system can cause a performance bottleneck. If the signals received by the logic analyzer are degraded, then the powerful triggering and analysis tools within the analyzer become useless.
The first consideration a designer must make when using a logic analyzer is to decide on the type of probing form factor. Probing connections come in two classes: "designed-in" and "after-the-fact." A designed-in probe has probing test points incorporated into the initial design, such as a connector-based or connectorless probe. An after-the-fact probe refers to systems in which testability isn't incorporated into the design. Rather, the connection is done with an individual probe tip that includes various interconnect accessories. One such example is the "flying-lead" probe.
Other issues designers must consider to achieve a successful logic-analyzer-probing connection include probe loading and signal quality. The article also delves into common problems associated with grounding (e.g., a ground lead that's too long; self-inductance of the ground loop) and presents preventative measures.
Finally, discussion surrounds two common problems that designers run into when using the wrong probing solution: probing at the wrong line location and choosing the wrong interconnect.
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