NASA Office of Logic Design

NASA Office of Logic Design

A scientific study of the problems of digital engineering for space flight systems,
with a view to their practical solution.

Independent NASA Test of
Actel SX-A, SX-S, and SX-SU
Field Programmable Gate Arrays (FPGAs)

KU1 Anomalies

Summary of KU1 Anomalies

S/N 50718 - Out of family ICCA


The mean ICCA for KU1 is 461 A with a standard deviation of 52 A.  S/N 50718 read approximately 1.8 mA.  While this value is within the specification value of 25 mA (ICCA + ICCI) the device was removed from the population prior to the beginning of the stress tests.  Preliminary analysis indicates that this is not a programmed antifuse related matter but is an internal short.  ESD is suspected and the failure analysis will be completed.


Additional Information.

S/N 50955 - Can not duplicate shift error


S/N 50955 passed initial ATE tests at both room and cold temperatures and subsequently failed at hot temperature prior to stress testing.  The unit failed initial bench level tests and was subjected to Schmoo testing on the ATE.  At this point the device was removed from the population prior to the beginning of the stress tests for further examination and then the device passed all tests.  The part was run in parallel with KU1, starting at step KU1-2, and will be closely monitored and then subjected to further analysis.


Chamber #3 Safety Shutdown

During the KU1-3 step, at the T = 115 hour point, Chamber #3 was operating in LTOL mode (-55 C) when all AC power was removed. Preliminary data indicates that this action was initiated by a safety interlock with a door being inadvertently opened. Data from the chamber, both sampled strip charts and oscilloscope monitors, is currently being reviewed for transients and additional chamber characterization testing is being performed.

50956: Delta Delay Anomaly


The KU1 set of devices was first subjected to two 250 hour test segments at +125 C.  These segments are designated KU1-1 and KU1-2.  The third test segment, also scheduled for 250 hours, was at -55 C, and is designated KU1-3.  Since the test was interrupted as a result of a safety shutdown, KU1-3 has been divided into two subsegments; KU1-3A will be the designator for the first 115 hours of test and KU1-3B will be the remaining 135 hours in the 250 hour KU1-3 block.  Following KU1-3A the KU1 lot was subjected to an ATE test.  One  unit, S/N 50956, while remaining within specification, was found to have propagation delay deltas that were relatively small in magnitude but out of family.  Testing and analysis are ongoing to determine whether or not the device has a fault, and if so, were chamber transient conditions from the unexpected shutdown a factor.  Note that there are a number of different structures that can produce effects such as an increase in propagation delay; the antifuse is only one such structure.

Analysis of S/N 50956 After KU1-3A

S/N 50985: Failed VIH (CMOS)


S/N 50985 failed VIH (CMOS) on the SET_N pin following step KU1-3B.  The device had previously been subjected to 500 hours at +125 C (KU1-1 and KU1-2) and then 115 hours at -55 C (KU1-3A).  KU1-3B was 55 hours at -55 C.

The VIH measurement was measured at 3.55V under room temperature conditions.  At VCCI = 5.0V, the specification limit is 3.5V under all conditions (70% of VCCI).  The unit was returned to the population, will be closely monitored, and is undergoing LTOL testing with KU1-3C.

S/N 50992: Failed VIH


After the completion of 1,250 hours of operation, S/N 50992 failed the VIH test at the end of step KU1-5 (+125 C).  An ICCA increase of approximately 1 mA was noted.

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Last Revised: February 03, 2010
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