8 Single-Event Transients (SET)

SETs are defined as heavy-ion-induced transients upsets on the OUT_X, the CS pin, and the FAULT pin of the TPS7H2140-SEP. SET testing was performed at room temperature (no external temperature control applied). The species used for the SET testing was ¹⁰⁹Ag for a LET_EFF = 48 MeV × cm² / mg. For more details, see Section 5. Flux of approximately 10⁵ ions / cm² × s and a fluence of approximately 10⁷ ions / cm² were used for the SET runs.

One unit was tested across multiple input and output conditions to determine the worst case setup for SETs. This unit was tested with a V_IN of 4.5, 12, and 28 V with loads of 2 A (0.5 A per channel) and 5.4 A (1.35 A per channel.) The worst case condition was found to be minimum V_IN (4.5 V) and a low load, 2 A (0.5 A per channel), was shown to be the worst case in transients for OUT_X, which is considered to be the most important signal. All five other units were only characterized at the worst case SET scenario.

OUT_X SETs were characterized using a window trigger of ±3% around the nominal output voltage. To capture the SETs, a MSO58B, two NI PXI-5172 scope cards, and one NI PXI-5160 scope card was used to continuously monitor OUT_X, CS, and FAULT. Each scope was operated independently from each other. The output voltage was monitored by using the TP12 and the TP14 test points on the board, while the CS was monitored using the TP10 test point, and FAULT from the TP9 test point.

The NI scopes were programmed to a sample rate of 10 M samples per second (S / s) and recorded 50 k samples, with a 20% pretrigger reference, in case of an event (trigger).

Under heavy-ions, the TPS7H2140-SEP exhibits three transient upsets that were fully recoverable without requiring external intervention.

1. A brief transient of the output voltage (referred here as V_OUT,SET). For the purpose of this report the transients were characterized for deviations –3% ≤ V_OUT ≤ 3% from the nominal output voltage.
2. A brief transient on the Current Sense (CS) pin. For the purpose of this report, the transients were characterized for deviations –4% ≤ V_CS ≤ 4% from the nominal output voltage. This type of SET is referred to here as V_CS,SET.
3. A V_FAULT upset ≤ nominal - 1 V on a negative-edge trigger.

Test conditions and results are listed in Table 8-3. Figure 8-2 shows typical time domain plots for all the different types of the observed SETs. Note that V_OUT was not monitored on the scope that V_CS was triggered from, and as a result, any V_CS drops due to a V_OUT,SET occurring cannot be classified.

Using the MFTF method shown in Single-Event Effects (SEE) Confidence Interval Calculations, the upper-bound cross-section (using a 95% confidence level) is calculated for the different SETs as shown in Table 8-2.

Figure 8-1 Typical V_OUT,SET

Figure 8-3 Typical FAULT_SET

Figure 8-2 Typical CS_SET