DATE: September 23, 2002
Here is the fifth in a series of OLD News articles.
Two Virtex devices were procured as flight parts and subject to a construction analysis. We used the XQVR300-4CB228V for our evaluation.
One item to note for users and reviewers of this system is that the manufacturer is cutting the conductor that grounds the lid. Depending on the application of the part, it is conceivable that the lid may charge up during operation and then discharge into a bond wire or the device, causing damage. Typically, our lids are grounded in flight to prevent this from happening, with drain wires being used for floating lids. The manufacturer will be offering the part with either grounded or ungrounded lids in the future. The cut is shown in Figure 1, below. The packaged part, both top and bottom, is shown in Figure 2.
Figure 1.
The gold trace coming from only one corner of the lid
identifies Pin 1. The manufacturer cut through the trace on
both of our samples, S/N 10 and S/N 15,
resulting in a floating
lid. The lid is soldered, providing a hermetic seal.
Figure 2.
Top and bottom views of one of the samples. The cut ground
is visible near pin 1.
The full construction analysis report can be viewed on-line at:
In my new OLD (Office of Logic Design) position, I am now making some of my informal e-mail lists semi-formal. These mailings will have pointers to tech tips that can [hopefully] proactively prevent errors from getting into flight designs or make things go faster and smoother. I have included an array of people from a number of number of organizations; different NASA Centers, ESA, etc., as you all may distribute to people in your own organizations and other colleagues. Please let me know if you are on this list in error or if someone should be added to it. This list is targeted towards those that either will design or review space flight digital electronics. Feel free to suggest topics for discussion and research or to contribute news items. [Note for this web-based release: to become a recipient on this mailing list, please send e-mail to: richard.b.katz@nasa.gov.]
All application notes are uploaded onto my www site. New additions are noted on the what's new page. I will give these mailings from time to time; too much and they will be filtered and ignored - too little and not enough information flows. So I'll try and hit a good balance.
Best regards,
-- rk
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