Many TPS7H410x-SP/SEP devices were characterized across voltage, load current, and LET_EFF by sweeping bias conditions up to the maximum recommended operating conditions. The purpose of this design of experiments (DOE) was to determine the bias conditions for the TPS7H410x-SP/SEP that fall within a safe operating area (SOA) where the device no longer experiences any destructive single-event effects (DSEE). The observed DSEE effect was a current latch which caused excess leakage on the input. Over the course of all SOA testing, the current latch ranged from 5mA of leakage up to 150mA of leakage. An example of a DSEE failure is shown in the SOA current plot below. In the case where the current latch occurred, the devices continued to operate normally aside from the incremented leakage current. Because the leakage current remained even after power cycling, this latch is considered a DSEE event. During the testing, only one variable was swept at a time while the other remained constant at the maximum recommended operating value. When collecting data for the DSEE SOA of the TPS7H410x-SP/SEP, it was observed that the probability of damaging a device was independent of temperature and output voltage, so data collection was conducted across both SEL and SEB testing at both VOUT = 1.2V and VOUT = 1.8V. Additionally, it was determined the SOA was similar for the TPS7H410x-SP at 75 MeV·cm²/mg as the TPS7H410x-SEP at 48 MeV·cm²/mg; therefore, the SOA results presented below include data from the TPS7H410x-SP and TPS7H410x-SEP.

Note that the DSEE results discussed in Section 7.2 and Section 7.3 were based on the findings of this SOA. The bias conditions these units were tested under were the maximum corners found by sweeping V_IN and I_OUT. The units tested inSection 7.2 and Section 7.3 were not included in the SOA tables below.

For LET_EFF ≤ 75 MeV·cm²/mg and load current of 3A, the maximum permissible input voltage to avoid DSEE is 6.5V. Maximum input voltage of 7V can be achieved at LET ≤ 75MeV·cm²/mg when the load current is decremented to ≤ 1.5A. A visual representation of the SOA curve can be observed in Figure 7-2. The green area encompasses the points where the TPS7H410x-SP/SEP can be operated at LET ≤ 75MeV·cm²/mg, with no damaged units observed. The yellow area represents where the TPS7H410X-SP/SEP is marginal and over the course of all testing only one unit had observable DSEE damage. The red area represents the points where DSEE was observed on multiple units and should be avoided to reliably use TPS7H410X-SP/SEP.

DSEE failures were observed under the red area. The cross-section for these event is extremely small (1.94×10^–8 to 3.69×10^–7).. During the SEE test campaign of the TPS7H410x-SP/SEP, 31 units were damaged from a total of 54 units tested. Table 7-2 shows the SOA results for the case where I_OUT was held at 3A and the V_IN was swept up. In the cases where V_IN was started <7V, V_IN was swept up by 100mV each run until either failing due to a DSEE event or because the unit reached the max recommended V_IN of 7V. Table 7-3 shows the SOA results for the case where V_IN was held at 7V and I_OUT was swept up. For each unit, the I_OUT was swept up by 500mA per run until the device had a DSEE event. Table 7-4 shows the calculated upper-bound cross section when combining the fluences for all runs with same load, voltage, and LET_EFF. The cross section values shown on the table calculated are calculated at 95% confidence interval (refer to SLVK047 for more details in the method used to calculate the upper bound cross section). Table 7-5 shows the passing bias conditions based on the SOA. As seen in Figure 7-2, the corners for the "green" condition are V_IN < 6.6V with an I_OUT/Channel = 3A and V_IN = 7V with an I_OUT/Channel < 2A, which is what the DSEE testing and results are based on in the respective SEL and SEB sections.