ICs target semiconductor test
Rick Nelson, Chief Editor -- Test & Measurement World, 10/1/2004
Texas Instruments is taking aim at semiconductor test, and other applications, with a series of off-the-shelf components. Targeting ATE makers such as Credence Systems, TI has just introduced the
THS4304 op amp, a 2.7- to 6-V single-supply device fabricated in TI's complementary bipolar SiGe process
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| Two single-supply THS4304 op amps can team up to drive a TI ADS5500 data converter. |
Test applications make up a small portion of the high-speed amplifier market and could become even smaller. Nossaman cites a study in which Databeans predicts that the high-speed amplifier market will increase from almost $700 million in 2004 to more than $1.2 billion by 2009. The market-research firm expects ATE unit shipments to increase only 8.1% during this period, vs. 15.2% for medical-imaging systems and 16.9% for cell-phone base stations.
Nevertheless, TI's Nossaman considers test a valuable niche, whose demanding customers push TI to extend performance limits. He cites low distortion as a key spec for the THS4304; it limits second-harmonic distortion to –85 dBc and third-harmonic distortion to –100 dBc.
For their part, tester makers can benefit from the low costs of parts that TI can produce in huge volumes. But it's the cost of an entire signal chain—not just one amplifier—that's critical.
Rolf Neuweiler, hardware R&D manager for Agilent Technologies' SOC platform division, comments, "We have looked and we are still looking into publicly available parts for our 93000 Series testers. What we've seen so far is that most of the parts, especially at the very high end, do not satisfy our needs in regard to the desired accuracy as well as cost." To help control costs, he says, Agilent fabricates chips necessary for 3.2-Gbps tester performance in silicon rather than SiGe.
Neuweiler elaborates on accuracy: "We need to take the distortion generated by the bandwidth-limiting signal path as well as the test socket into consideration. To compensate for these effects we've got our own IP, which we build into our pin-electronics chips."
Neuweiler also says, "On the very high end, it's mandatory to distribute the functional blocks of the channels onto those chips where it makes the most sense." For example, he says, most of each tester channel's complex timing system resides in Agilent's highly integrated CMOS "Test Processor per Pin," while the parts that need to run at 3 GHz and above go into a high-speed bipolar front-end IC.
Neuweiler does add, though, that sometimes Agilent engineers will modify an off-the-shelf design to meet their needs. What's key for test-equipment customers is that ATE vendors have an increasingly capable array of standard and proprietary devices that they can mix and match to meet the price/performance points your test applications demand.
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