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)

KM2 Anomalies

• S/N 38014: t_PD anomaly

• S/N 27869: I/O Monitor Not Toggling

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S/N 38014: t_PD anomaly

Summary:

S/N 38014 was observed to have a t_LH anomaly at the conclusion of KM2-4 (+125 ºC). Previously, the device had been subjected to 750 hours of +125 ºC testing.  The magnitude of the delta delay anomaly was approximately 10 ns.  Diagnostics have shown that the antifuse fault is on a net with a single S-type antifuse.

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S/N 27869: I/O Monitor Not Toggling

Summary

S/N 27869 successfully completed 1,000 hours of HTOL (+125 ºC): KM2-4.  After the completion of KM2-5 (LTOL, -55 ºC) it was observed that the I/O monitor was not toggling during the 50 MHz test.  No other problems were noted.

During troubleshooting the anomaly went away and the root cause could not be determined.

Analysis and Discussion

• History
  • S/N 27869 passed all testing post 1000 hours HTOL (+125 ºC)
• ATE Testing
  • S/N 27689 failed ATE testing for the 50 MHz functional test post 250 hours LTOL (-55 ºC)
    • Delay and 1 MHz functional tests passed
  • Failure was observed only on the IO_Monitor pin.
• Bench Testing
  • S/N 27869 and a reference unit was verified on the bench at 1 MHz, with V_CCA = 2.5V
  • Test frequency was changed to 3 MHz.
    • S/N 27869 failed
    • Reference unit passed
  • V_CCA increased to 3.0V
    • S/N 27869 passed
    • Suggests a setup time problem
  • V_CCA decreased back to 2.5V
    • S/N 27869 still fails
  • Units power cycled
    • S/N 27869 verified on the bench at 50 MHz, with V_CCA = 2.5V
    • S/N 27869 operated normally from 1 MHz to 50 MHz (V_CCA = 2.3V to 2.5V)
• ATE Testing
  • S/N 27869 passed all ATE testing criteria post bench verification

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