During the SEL testing the device was heated to 125°C by using PID controlled heat gun (MISTRAL 6 System (120V, 2400W)). The temperature of the die was constantly monitored during testing at TAMU through an IR camera integrated into the control loop to create closed-loop temperature control. The die temperature was verified using a standalone FLIR thermal camera prior to exposure to heavy ions at KSEE.

The species used for the SEL testing was ¹⁰⁹Ag (TAMU) at 15 MeV/nucleon and ¹⁰⁹Ag (KSEE) at 19.5 MeV/nucleon. For both ions an angle of incidence of 0° was used to achieve a LET_EFF of ≈ 48 MeV×cm²/mg (for more details refer to Table 5-1). The kinetic energy in the vacuum for ¹⁰⁹Ag (TAMU) is 1.635 GeV and ¹⁰⁹Ag (KSEE) is 2.125 GeV. Flux of ≈10⁵ ions/cm²/s and a fluence of ≈10⁷ ions/cm² per run was used. Run duration to achieve this fluence was ≈2 minutes. The seven devices were powered up and exposed to the heavy-ions using the maximum recommended input voltage of 14V with the maximum recommended load of each respective device. No SEL events were observed during all seven runs, indicating that the TPS7H401x-SEP is SEL-free up to 48 MeV×cm²/mg. Table 8-4 shows the SEL test conditions and results. Figure 7-1 shows a plot of the current versus time for run 3.

Using the MFTF method shown in Single-Event Effects (SEE) Confidence Interval Calculations and combining (or summing) the fluences of the seven runs at 125°C (7 × 10⁷), the upper-bound cross-section (using a 95% confidence level) is calculated as: σ_SEL ≤ 5.27 × 10^-8 cm²/ device for LET_EFF = 48 MeV×cm²/mg and T=125°C.