In Situ Parametric and Functional Testing for Total Ionizing Dose Testing

1. In Situ Parametric and Functional Testing for Total Ionizing Dose Testing Igor Kleyner Orbital Sciences Corp. Rich Katz NASA Goddard Space Flight Center

2. Overview • Traditional approach to TID testing • First generation of “K-Labs” TID test system • Second generation of “K-Labs” TID test system • Remote control and easy access to real time data • Flexibility of test configuration • In situ monitoring, functional and parametric testing

3. Step Irradiation Procedure • Device Under Test (DUT) is tested before irradiation, exposed for a certain amount, then tested again • The cycle is repeated until DUT receives required dose of radiation • DUT is statically biased with power supplies • No control or monitoring of DUT in the chamber • Very costly and labor-intensive process • Potentially introduces aliasing problem since DUT behavior inside the chamber is not monitored • Lack of observation leads to lack of understanding, including failure mechanisms and their manifestations during the test

4. First Generation “Stupid” System • Consisted of • DOS-based PC running rather simple software • Power Supply for biasing DUTs • Software • monitors power supply over General Purpose Interface Bus (GPIB) • records bias currents in a log file • The system produced reliable results of good quality for TID testing of various FPGAs and other devices

5. Shortcomings of First Generation “Stupid” System • DOS-based, lack of friendly user interface • Lack of flexibility, any change in configuration required software editing and recompilation • Bias current is the only parameter monitored • Operator’s presence at test site is required in order to make necessary adjustments/decisions during the test

6. Second Generation “Stupid” SystemGoals • Flexibility and expandability to allow for various laboratory instruments to be “plugged in” the system to satisfy requirements of a particular test • Remote control of the test • Remote monitoring of the test over the Internet • Real-time data processing, graphs and/or raw data posted on the web site as the test progresses • In situ functional and parametric testing capabilities

7. Lab Instrument 1 Lab Instrument 2 Lab Instrument 3 Lab Instrument 4 Second Generation System - Overview WWW TID Chamber Building TID Chamber DUT “K-labs” GPIB GSFC network “rk” Server “Stupid” PC Test Control PC

8. “Stupid” - User Interface and Capabilities • Windows 95-based user-friendly Interface • Runs Strip-chart of all Voltages and Currents • Executes remote commands • Monitors chamber conditions • “Stupid” can be configured to control various lab instruments over HPIB • Power Supply • Signal Generator • Multimeter • Digital Oscilloscope

9. “Stupid” - Flexible Test Configuration

10. Test Control PC • Can be located anywhere on GSFC computer network • Issues commands for “Stupid” at selected time intervals (or at operator’s discretion) by uploading a command file to “Stupid” PC. • Commands may include • “dump” strip-chart data • send a number of pulses to DUT • measure DUT output voltage • capture and digitize a waveform, etc. • Downloads requested data from “Stupid” • Creates charts and text data files for real-time test monitoring and web posting and post-test analyses.

11. Charts and Raw Data Posted on “rk” Web Site

12. In Situ Functional Testing • Traditional approach for antifuse-based FPGAs relies exclusively on bias current monitoring • Earlier families of Actel FPGAs (Act1, Act2, Act3) usually show ICC increasing exponentially to relatively high levels (>100 mA) before any irregularities (i.e. high current spikes) are observed; such “spikes” are usually a reliable indication of a functional failure • Initial testing of devices from SX family showed presence of “suspicious” small jumps in ICC current at relatively low current levels ( 10 to 50 mA)

13. In Situ Functional Testing Example 1 • Actel antifuse-based FPGA device (RT54SX16) • Traditional test configuration (ICC strip-chart) is expanded to include in situ short functional test • Signal Generator is utilized to send stimulus signal(s) to the DUT • Output Voltage(s) are measured by Multimeter • The sequence is executed automatically at programmed time intervals and/or manually as desired by experimenters; functional test results are posted on the web site for convenient monitoring along with ICC strip-chart data • The test, and other subsequent tests of SX family devices, showed that the first small jump in the ICC level usually occurs immediately the functional failure of a DUT

14. Actel SX Family Device in situ Functional Failure Functional failure occurred at ~15mA; followed by immediate short current spike

15. In Situ Functional Testing Example 2 • Two Actel SX family devices (same lot, dose rate) irradiated simultaneously. • S/N LAN3403 configured traditionally (static, basic functional test once per hour) - “Static” configuration • S/N LAN3404 is clocked continuously at 1kHz -“Dynamic” configuration • Dynamic device fails at ~8% lower total accumulated dose level than static device “Dynamic” device failure “Static” device failure

16. Parametric In Situ Testing Example 1 • Flash-based FPGA device (Actel A500K050) • Initial testing involved standard elements • ICC monitoring • In situ basic functional test • Post-irradiation parametric testing showed significant increase in Propagation Delay (tPD) • Consequently, in situ measurement of tPD was added to the test configuration • Signal Generator supplies input pulse for DUT • Waveforms are captured by Digitizing Oscilloscope and tPD is measured

17. In Situ measurement of Propagation Delay Real-time Digitized Input and Output Waveforms Before irradiation : tPD = 135ns After accumulating 90 krad : tPD = 260ns

18. Compiled tPD Measurement Data

19. Parametric In Situ Testing Example 2 • Low Voltage Dropout Regulator (LM2931CT) • DUT was irradiated at nominal supply voltage (5 V) • Output Voltage strip-charted • In situ parametric testing: • Input Voltage sweep (from 6 V to 3 V) performed • Output Voltage measured and recorded for each sweep

20. LVDO Regulator Transfer Characteristics Obtained at Various Points during the Test

21. Conclusions/Lessons Learned • In situ functional and parametric testing are valuable and indispensable tools for high-quality TID testing of modern FPGAs • Remote control and monitoring capabilities are essential for producing reliable test data with limited labor resource.