Actel Power Supply Transient Evaluation on RTAX-S/SL and RTSX-SU Devices Solomon Wolday, Roopa Kaltippi, Antony Wilson September 2, 2009

Actel Corporation © Agenda  Background  Experiment Vehicles  RTAX2000S and RTSX72SU  Enhanced Antifuse Qualification (EAQ) design  Summary of Experiments  RTAX-S/SL Summary  RTSX-SU Summary  Additional Reliability Testing  Conclusion

Actel Corporation © Background  Single Event Effect (SEE) events can cause momentary power supply transients on third-party RH power regulators  The output of the regulator can be as high as the regulator input  The high transient voltages last for durations on the order of microseconds  This results in overstress for all devices powered by these regulators  Investigations were completed by Actel to study the effects of the overshoots  This presentation summarizes the experiments and data collected

Actel Corporation © Experiment Vehicles  Experiments were completed on RTAX-S/SL and RTSX-SU devices  Devices from multiple wafer lots were stressed thereby eliminating process variations  RTAX2000S-CQ352B  Second largest device in the RTAX-S/SL device family  Same device used for the qualification of initial RTAX-S qualification  Devices programmed with the EAQ design  Design utilizes 98.6% of device logic  RTSX72SU-CQ256B  The larger device in the RTSX-SU device family  Same device and package used for the RTSX-SU qualification  Devices programmed with EAQ design  Design utilizes 99.9% of device logic

Actel Corporation © EAQ Design Overview  Enhanced Antifuse Qualification (EAQ) design  Design used for study of antifuse reliability experiment  EAQ design has four different test blocks

Actel Corporation © EAQ Design Overview (Cont’d)  EAQ design fully utilizes device logic  Design has high perceptibility delay measurements  Multiple delay lines of combinatorial modules per device  Design exercises all device features  Array test block  Covers registers and combinatorial logic  I/O test block  Covers both input and output buffers of each I/O  RAM test block  Utilizes all SRAM blocks in the devices  All logic and I/O toggled during stress experiment

Actel Corporation © Stress Setup  Setup used to stress the RTAX-S/SL and RTSX- SU devices  Setup ensures that there is no current limiting during stress  Device Under Test (DUT) stressed with exact applied stress pulse  Enables flexibility to control stress amplitude and duration  Stress applied on one power supply at a time

RTAX-S Stress

Actel Corporation © RTAX-S/SL AC Transient Stress  RTAX-S/SL nominal operating conditions  Both V CCA and V CCI /V CCDA power supplies were stressed  Stress applied separately on the two power supply levels  Clocks were running at 20MHz during these experiments  Functionality of devices also monitored during stress Power SupplyNominal Level V CCA 1.5V V CCI 3.3V V CCDA 3.3V

Actel Corporation © RTAX-S/SL AC Transient Stress (Cont’d)  Devices were programmed with the EAQ design  All stress tests were performed at room temperature  Pre and post stress functional and parametric data collected  Delta calculations performed for each parametric test  26 RTAX2000S devices were stressed with above conditions  Devices collected from 2 different wafer lots  All 26 devices passed functional parametric testing  No out of family delay shifts or parametric deltas were observed  Summary of test results below Number of DeviceAC Stress LevelResult 26V CCA = 4.0VPass 26V CCI /V CCDA = 6.0VPass

Actel Corporation © RTAX-S/SL DC Stress  Both V CCA and V CCI /V CCDA power supplies were stressed  V CC increased from nominal level by increments of 0.1V  Clocks were running at 20MHz during these experiments  Summary of test results shown below Number of DeviceDC Stress LevelResult 26V CCA = 3.5VPass 26V CCI /V CCDA = 5.5VPass

RTSX-SU Stress

Actel Corporation © RTSX-SU AC Transient Stress  RTSX-SU nominal operating conditions  Both V CCA and V CC power supplies were stressed  Clocks were running at 20MHz during these experiments  Functionality of devices also monitored during stress Power SupplyNominal Level V CCA 2.5V V CCI 5.0V

Actel Corporation © RTSX-SU AC Transient Stress (Cont’d)  Devices were programmed with the EAQ design  All stress tests were performed at room temperature  Pre and post stress functional and parametric data collected  Delta calculations performed for each parametric test  27 RTSX72SU-CQ256 devices were stressed with above conditions  Devices collected from 3 different wafer lots  All 27 devices passed functional parametric testing  No out of family delay shifts or parametric deltas were observed  Summary of test results below Number of DeviceAC Stress LevelResult 27V CCA = 5.5VPass 27V CCI = 7.5VPass

Actel Corporation © RTSX-SU DC Stress  Both V CCA and V CCI power supplies were stressed  V CC increased from nominal level by increments of 0.1V  Clocks were running at 20MHz during these experiments  Summary of test results shown below Number of DeviceDC Stress LevelResult 27V CCA = 4.5VPass 27V CCI = 6.5VPass

Actel Corporation © Additional Reliability Testing  All devices in the preceding experiments were then processed through Group C life test  To understand long term reliability concerns  Dynamic programmed burn-in at maximum specified V CC conditions  Group C experiments completed with 1000hrs burn-in at ambient temperature of 125°C  Functional and parametric data analysis completed at 168hrs and 500hrs pull-points  All devices passed functional and parametric tests  No out of family deltas or parametric shifts were observed

Actel Corporation © RTAX-S/SL and RTSX-SU Damage Levels  Additional experiments were completed to determine voltage levels at which permanent damage occurs  Damage was only possible with DC stress  AC transient stresses were not able to cause damage with available setup  Damage only occurred on V CCA supplies  Permanent damage levels  I CC increase and functional failures were observed at damage levels Device V CCA Nominal Level Damage Level RTAX-S/SL1.5V5.0V RTSX-SU2.5V6.0V

Actel Corporation © Conclusion  Devices were stressed beyond their absolute maximum rated conditions using DC and AC stress  Outcome of the study indicates RTAX-S/SL and RTSX-SU devices are robust and reliable  RTAX-S/SL devices withstood AC transients exceeding nominal voltages by 1.8X on V CCI /V CCDA and 2.6X on V CCA  RTSX-SU devices withstood AC transients exceeding nominal voltages by 1.5X on V CCI and 2.2X on V CCA  Customers are still advised against stressing beyond the conditions outlined in the datasheet  The RTAX-S and RTSX-SU are designed to withstand high voltages applied during programming  Far more tolerant to voltage overshoots than other technologies