K.A. LaBel
CODE 735.1
NASA/GSFC
Greenbelt, MD 20771C.M. CRABTREE
Hughes/STX
Lanham, MD 20706
I. INTRODUCTION
The objective of this study was to determine the threshold linear energy transfers (LETths) and cross-sections for single event upset (SEU) and single event latchup (SEL) due to heavy ions. SEU LETth is defined as the minimum LET value to cause an effect at a fluence of 1E7 particles/cm2. SEL LETth is defined as the maximum LET value at which no latchup occurs at a fluence of 1E7 particles/cm2.
II. TEST SAMPLES
Relevant characteristics of the devices are summarized in the following table:
Device Type Mfg. Date Code Technology
CP2420 Crosspoint CMOS FPGA
Sample devices were delidded in order to accommodate beam penetration limits of the test facility.
III. TEST TECHNIQUES AND SETUP
A. Facility Usage
The test facility used was the Brookhaven National Laboratories (BNL) Single Event Upset Test Facility (SEUTF) between January 6 and 7, 1994. This setup utilizes a dual Tandem Van De Graaff accelerator suitable for providing ions and energies for SEU testing. The test devices are mounted on a device-under-test DUT) board inside a vacuum chamber.
The SEUTF uses a computer-driven monitor and control program to provide a user-friendly interface for running the experiments. Additionally, support was provided by engineers working for Code 300. Hard copies of the test data and graphs were also made available.B. Test Hardware, Software and Control
Test hardware, software, etc,... consisted of a DUT board placed in the test chamber, six feet of twisted pair ribbon cable, and two PC-based testers, the Omnilab and VXI systems. Both testers provide test patterns to the test boards and are capable of capturing output when errors occur. The VXI enhances the error capture by using an intrinsic compare and a custom-built FIFO buffer board thereby reducing processing time and eliminating the need for additional hardware on the DUT boards. Both systems are capable of controlling the entire test setup, digital counters, power supplies, waveform generators as well as the BNL computer via an IEEE 488 bus.
C. Device Test Procedure
The test procedure was similar for all devices tested. All tests were dynamic in nature, meaning that the devices were operating during the test as they would in a spacecraft application. First, a stimulus pattern was then loaded to the device. Power was then supplied and the device began to function normally while exposed to the ion beam. Inputs from the device were constantly monitored by either the Omnilab or VXI and all errors accumulated until either fluence was reached or a latchup condition occurred. In the case of the latter, power and beam to the device were terminated and the test run ended prematurely. Otherwise, error counts were logged to the hard drive. All DUTs were tested under a (nominal) 25 degrees celsius.
D. Ion Beam Usage
The following table summarizes the ions used for testing.
ION ATOMIC # ENERGY, MeV LET, MeV*cm2/mg at 0 deg.
- F 19 139.3 3.44
- Cl 35 212 11.3
- Ni 58 262.8 26.9
- Au 197 340.4 82
Additional effective LET values were attained by varying the angle of incidence of the ion beam to the device. All LETs discussed are in MeV*cm2/mg.
IV. RESULTS AND DISCUSSIONS
CP2420
Figure 9 <not yet included> shows the SEU cross section per bit and latchup cross section per device versus the test LET value for all DUTs. The LET threshold for zero upsets is ~12.5. Both samples latched up at an LET of 26.6. Since no LET values between 15 and 26.6 could be attained, the latchup threshold is between those two values.
V. SUMMARY
Generally, devices demonstrating an SEL LETTH < 35 are not recommended as candidates for space applications. Falling into this category is the CP2420.
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