For Good Measure

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How do you achieve high bandwidth in your measurements while minimizing current load on your DUT? Given that your DUT is a power rail, you really don't want to draw too much current from it., or your measurement system will distort the rail. But these two measurement criteria are at loggerheads with each other. It's a quandary, and it has to do with the fundamental nature of signals on interconnects.

Measuring the noise on a power rail seems to be a straightforward task. However, there are some basic pitfalls that can cause incorrect, or even downright strange, results. Let's look at one of these challenges: RF pickup. We'll demonstrate the effect of RF pickup on a power-rail measurement, and then we'll show you an effective means of mitigating that effect.

Now in its fourth generation, which sports data-transfer rates up to 16 Gb/s, Peripheral Component Interface Express standard (PCI Express, or PCIe) requires challenging physical-layer test requirements (Figure 1). We've covered electrical compliance test for PCIe 3.0 in some detail, but with the test specifications for PCIe 4.0 rounding into shape, it's time for a deep dive into electrical compliance test for this ubiquitous peripheral interface protocol.

In this DDR 101 introductory piece, learn about the fundamentals of a DDR interface and some basics of physical-layer testing.