013_EETE

EETE JULAUG 2012

SPOTLIGHT Can You Meet Today’s Budget Requirements While Anticipating Tomorrow’s Bandwidth Requirements? It’s the never-ending dilemma: trying to But as you can see in Figure 1, a 500 MHz scope keep your equipment costs as low as possible in essentially turns your digital bit stream into what the short term, knowing that your next generation appears to be an overlay of sinusoids, obscuring vital of designs will probably require faster and more- signal details. Clearly, a bandwidth of only 500 MHz advanced test and measurement capabilities. can’t capture and measure these signals accurately. Deciding how much to buy and Figure 2,made on the same signal with a 1 GHz when to upgrade scope, gives a much more realistic representation of the bit stream, thereby accelerating your search for Oscilloscopes, for instance, present a fairly linear the insights you need. tradeoff between price and bandwidth, a key Figure 1 performance specification. More bandwidth is great Moving up without starting over A 500 MHz scope proves inadequate for to have, but budget pressures often limit you to this DDR2-667 signal; the eye diagram buying only as much as you need for your immediate The Agilent InfiniiVision 3000 X-Series oscilloscopes presents what appears to be an overlay projects. are built on the premise that you need to man- bit stream.of sinusoids but should really be a digitalage your budgets carefully today and anticipate In addition to the price/performance question, it’s performance requirements on future projects, too. vital to have a clear understanding of how much The newest 1 GHz model starts at the lowest price in bandwidth your current—and future—applications the industry. And if you plan to buy or already own a really require. lower bandwidth 3000 X-Series scope, your invest- ment is protected—they are all fully upgradable to As an example, let’s say your last embedded design the new 1 GHz level. Buy as much performance as used DDR1 memory (which clocks data into and out you need for today’s designs, then easily upgrade to of memory on both the rising and falling edges of the meet tomorrow’s requirements. clock signal) with data transfer rates in 200 Mbps range. If you used a scope with 500 MHz bandwidth To learn more about how to identify the necessary to capture and verify critical timing parameters, this bandwidth for your specific measurement instrument probably offered sufficient measurement applications, visit Figure 2 accuracy. www.agilent.com/find/evaluatingbandwidth measured with a 1 GHz scope; the eyeHere’s that same DDR2-667 signal However, your next design will be based on higher Bandwidths for your Application.” digital bit stream.diagram now clearly displays the overlaid“Evaluating Oscilloscopeand download speed DDR2 technology. Will that 500 MHz band- width still do the job? The eye diagram, which provides a composite picture of signal quality by overlaying high and low bits to InfiniiVision 3000 X-Series determine when data is valid, is a common measure- oscilloscopes ment performed on read and write data signals of DDR memory. • New! 100 MHz to 1 GHz bandwidth, up to 4 Mpts memory, DSO and MSO models Figure 1 shows an example of an eye-diagram • 8.5-inch WVGA display is 50% larger measurement using a 500 MHz scope on a and 3x the resolution of competitive scopes data signal representative of DDR2-667 memory. • Hardware-based measurement applications including serial decode While the clocking rate of DDR2-667 memory is • Up to 1,000,000 waveform updates/second with MegaZoom technology 667 MHz, both the clock signal and the maximum • Fully upgradable—bandwidth, MSO, memory up to 4 Mpts, measurement toggle rate of the data signal are only 333 MHz. applications, WaveGen built-in 20 MHz function and arbitrary waveform One might assume, then, that a 500 MHz scope generator, and integrated digital voltmeter would provide sufficient bandwidth to capture and measure these signals. Get a quick quote today at www.agilent.com/find/quick-quote


EETE JULAUG 2012
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