During the SEL characterization, the device was heated using the load (0.6V case) or with external heat (13.3V case). When using external heat, the device was heated to 125°C by a cool-touch heat gun controlled by a Variac at MSU and a Closed-Loop PID controlled heat gun (MISTRAL 6 System (120V, 2400W) at TAMU. The temperature of the die was verified using FLIR IR camera prior to exposure to heavy ions.

The species used for SEL testing were Thulium (¹⁶⁹Tm at 20MeV/nucleon, MSU facility) and Holmium (¹⁶⁵Ho at 15 MeV/nucleon, TAMU facility). For both ions an incident angle of 0° was used to achieve an LET_EFF = 75 MeV·cm²/mg (for more details refer to Ion LET_EFF, Depth, and Range in Silicon). The kinetic energy in the vacuum for ¹⁶⁹Tm is 3.431 GeV and ¹⁶⁵Ho is 2.474 GeV. Flux of 5.90 x 10⁴ to 9.99 x 10⁴ ions/cm² ·s and a fluence of approximately 10⁷ ions/cm² per run was used. Run duration to achieve this fluence was between 2-4 minutes. The six units were powered up and exposed to the heavy-ions using the maximum recommended input voltage of 14V. No SEL events were observed during all six runs, indicating that the TPS7H1121-SP is SEL-free up to 75 MeV·cm²/mg. Table 8-4 shows the SEL test conditions and results. Figure 7-1 and Figure 7-1 show plots of the current vs time for runs #1 and #3.

Using the MFTF method described in Single-Event Effects (SEE) Confidence Interval Calculations application report and combining (or summing) the fluences of the six runs at 125°C (6 × 10⁷), the upper-bound cross-section (using a 95% confidence level) is calculated as:

σ_SEL ≤ 6.15 x 10^-8 cm²/device for LET_EFF = 75 MeV·cm²/mg and T = 125°C.