Application Note 1938 Single Event Effects (SEE) Testing of the ISL71091SEHxx Precision Voltage References Family Introduction SEE Test Objectives The intense proton and heavy ion environment encountered in space applications can cause a variety of single event effects in electronic circuitry, including Single Event Upset (SEU), Single Event Transient (SET), Single Event Functional Interrupt (SEFI), Single Event Burnout (SEB). SEE can lead to system-level performance issues including disruption, degradation and destruction. For predictable and reliable space system operation, individual electronic components should be characterized to determine their SEE response. This report discusses the results of SEE testing performed on the ISL71091SEHxx product family or precision references design for space applications. The ISL71091SEHxx was tested to determine its susceptibility to Single Event Burnout (SEB, destructive ion effects) and to characterize its Single Event Transient (SET) behavior over various Linear Energy Transfer (LET) levels. Product Description The ISL71091SEHxx is a family of ultra low noise, high DC accuracy precision voltage reference products with an input range to 30V. Four output voltage variants are available, 3.30V (ISL71091SEH33), 2.048V (ISL71091SEH20), 4.096V (ISL71091SEH40), and 10.0V (ISL71091SEH10). The ISL71091SEHxx use the Intersil PR40 Advanced Bipolar technology to achieve sub 4µVP-P noise at 0.1Hz and achieve 0.25% accuracy over radiation. Its implementation in an advanced bonded wafer SOI process using deep trench isolation results in fully isolated structures and latch-up free performance, whether electrically or single event (SEL) caused. Product Documentation For more information about the ISL71091SEHxx, refer to the following documentation. Testing was performed at the Texas A&M University (TAMU) Cyclotron Institute heavy ion facility. This facility is coupled to a K500 super-conducting cyclotron, which is capable of generating a wide range of test particles with the various energy, flux and fluence levels needed for advanced radiation testing. SEE Test Set-up SEE testing is carried out with the sample in an active configuration. A schematic of the ISL71091SEHxx SEE test fixture is shown in Figure 1. The test circuit is configured to accept an input voltage from 4V to 30V and generate the nominal output voltage. The output current of the reference was adjusted using fixed load resistors on a test board. Four ISL71091SEHxx test fixtures were mounted to a test jig, which could be moved with respect to the ion beam. The parts were assembled in dual in-line packages with the metal lid removed for beam exposure. Using 20-foot coaxial cables, the test jig was connected to a switch box in the control room, which contained all of the monitoring equipment. The switch box allowed any one of the four test circuits to be controlled and monitored remotely. In later testing a single board with four devices mounted so that all four could be exposed to the ion beam at once. This allowed testing of four parts simultaneously. • ISL71091SEHxx datasheets: - ISL71091SEH33 (3.300V) - ISL71091SEH20 (2.048V) - ISL71091SEH40 (4.096V) - ISL71091SEH10 (10.00V) • Standard Microcircuit Drawing (SMD): 5962-14208 • ISL71091SEHxx Application Note: - AN1906 “ISL71091SEHXXEV1Z User’s Guide” June 4, 2014 AN1938.0 SEE Test Facility 1 Digital multimeters were used to monitor input voltage (VIN), output voltage (VOUT) and input current (IIN). LeCroy waveRunner 4-channel digital oscilloscopes were used to capture and store SET traces at VOUT that exceeded the oscilloscope trigger level. CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures. 1-888-INTERSIL or 1-888-468-3774 | Copyright Intersil Americas LLC 2014. All Rights Reserved Intersil (and design) is a trademark owned by Intersil Corporation or one of its subsidiaries. All other trademarks mentioned are the property of their respective owners. Application Note 1938 1 2 TP3 TP6 GND 7 3 3 6 6 4 4 5 5 3 8 7 TP7 VOUT TP8 TRIM TP5 ISL7109XSEH C3 TP2 8 2 1000PF C2 TP4 1 2 4 SP2 1 2 GND 4 SP3 OPEN 0.1UF COMP 1 VOUT 3 VIN 1 2 TRIM3 C4 3 U1 1UF 1 2 TP1 C1 5BNC1 TRIM2 SP1 4 GND VOUT 3 4 TRIM1 GND TP9 FIGURE 1. SCHEMATIC OF THE ISL71091SEHXX SEE TEST CIRCUIT NOTE: 1. The output capacitor (COUT), C4, was varied between 0.1µF and 10µF and the compensation capacitor (CCOMP), C2, was varied between 1nF and 10nF. SEB Testing of ISL71091SEH33 (3.3V) Reference For the SEB tests, conditions were selected to maximize the electrical and thermal stresses on the Device Under Test (DUT), thus insuring worst-case conditions. The input voltage (VIN) was initially set to 35V, and then increased in 1V increments. SEB testing was conducted with the ISL71091SEH33, hence the output voltage (VOUT) was 3.3V. Output current (IOUT) was set to either 5mA (sinking current) or 10mA (sourcing current), which are the limits of load regulation current for the parts. The output capacitance was tested at both 0.1µF and 10µF. Case temperature was maintained at +125ºC by controlling the current flowing into a resistive heater bonded to the underside of the DUT. This insured that the junction temperature of the DUT exceeded +125ºC, which is the maximum junction temperature anticipated for high reliability applications. Four devices were irradiated with Au ions at a normal incident angle, resulting in an effective LET of 86.4 MeV•cm2/mg. Table 1 summarizes the results of SEB testing. The chart shows sample size and passing results for an input voltage level of 36V on each device. From a silicon design perspective all the products in the ISL71091SEHxx product family are exactly the same in silicon. The output voltages are produced by the same circuitry and trimmed through a resistor ladder network. Therefore, the ISL71091SEH33 SEB results are applicable to the complete product family of ISL71091SEHxx parts. TABLE 1. ISL71091SEH33 SEB TEST RESULTS TEST ID DEVICE # VIN VOUT PRE VOUT POST VOUT DELTA (%) IOUT (A) COUT (µF) PRE SEE IIN (mA) POST SEE IIN (mA) DELTA IIN (%) 401 1 35 3.3284 3.3286 0.01% -0.005 0.1 0.3312 0.3311 -0.03 2 35 3.3004 3.3003 0.00% 0.01 0.1 10.593 10.591 -0.02 3 35 3.3022 3.3016 -0.02% 0.01 10 10.539 10.535 -0.04 4 35 3.3252 3.3249 -0.01% -0.005 10 0.3274 0.3246 -0.86 1 36 3.3286 3.3284 -0.01% -0.005 0.1 0.3316 0.3316 0.00 2 36 3.3003 3.3001 -0.01% 0.01 0.1 10.591 10.589 -0.02 3 36 3.3016 3.3015 0.00% 0.01 10 10.535 10.534 -0.01 4 36 3.3249 3.3248 0.00% -0.005 10 0.3252 0.3236 -0.49 1 38 3.3284 4.3 29.19% -0.005 0.1 0.3324 na 2 38 3.3001 0.0012 -99.96% 0.01 0.1 10.589 na 3 38 3.3015 3.3009 -0.02% 0.01 10 10.534 10.528 -0.06 4 38 3.3248 4.0779 22.65% -0.005 10 0.3245 na 402 403 Submit Document Feedback 2 AN1938.0 June 4, 2014 Application Note 1938 TABLE 1. ISL71091SEH33 SEB TEST RESULTS (Continued) TEST ID DEVICE # VIN VOUT PRE VOUT DELTA (%) VOUT POST IOUT (A) COUT (µF) PRE SEE IIN (mA) POST SEE IIN (mA) DELTA IIN (%) NOTE: 2. Samples were tested with increasing input voltage (VIN) until failure as determined by more than 1% change in either VOUT or IIN. The chart shows passing results for the input voltage levels of 35V and 36V and failures at 38V. Each irradiation was to 5x106 ions/cm2 at a rate of 2.5x104 ions/(cm2s). The first SET testing of the ISL71091SEHxx family was done on four samples of the ISL71091SEH33. Two parts had COUT = 0.1µF and two parts had COUT = 10µF. Irradiation was done at room temperature with LET of 8.5, 28, and 60 MeVcm2/mg. Samples had VIN varied over 5.5V to 16.5V. VIN was limited to 16.5V due to the observed large SET at VIN = 30V which still represented in Figure 3 at VIN = 16.5V. Table 2 shows the SET summary giving the cross section for each input voltage and LET level. Figure 2 is the LET threshold plot representing Table 2. TABLE 2. SET SUMMARY OF ISL71091SEH33 (3.3V) SAMPLES COUT (µF) SET COUNT NET FLUENCE (p/cm2) CROSS SECTION (cm2) LET VIN IOUT (mA) 60 16.5 1 10 71 1.0E+07 7.1E-06 60 16.5 1 10 11 1.0E+07 1.1E-06 60 13.2 1 0.1 2661 1.0E+07 2.7E-04 60 13.2 1 0.1 2558 1.0E+07 2.6E-04 60 5.5 1 0.1 1806 1.0E+07 1.8E-04 43 16.5 1 0.1 1817 1.0E+07 1.8E-04 43 13.2 1 0.1 1629 1.0E+07 1.6E-04 43 5.5 1 0.1 1238 1.0E+07 1.2E-04 28 16.5 1 0.1 672 5.0E+06 1.3E-04 28 13.2 1 0.1 676 5.0E+06 1.4E-04 28 11 1 0.1 662 5.0E+06 1.3E-04 28 5.5 1 0.1 572 5.0E+06 1.1E-04 8.5 16.5 1 0.1 188 5.0E+06 3.8E-05 8.5 13.2 1 0.1 191 5.0E+06 3.8E-05 8.5 5.5 1 0.1 158 5.0E+06 3.2E-05 NOTE: 3. Trigger level for the output voltage was set to ±30mV and CCOMP = 1nF. 3.0E-04 SET (±33mV) CROSS SECTION (cm2) SET Testing of ISL71091SEH33, 3.3V Reference VIN = 13.2 2.5E-04 2.0E-04 VIN = 16.5 1.5E-04 VIN = 11 VIN = 5.5 1.0E-04 5.0E-05 0.0E+00 0 10 20 30 40 50 ION LET (MeV·cm2/mg) 60 70 FIGURE 2. ISL71091SEH33 LET THRESHOLD PLOT FOR ±30mV TRIGGER WINDOW WITH COUT = 0.1µF AND IOUT = 1mA. The data presented above only counts SET that exceed ±30mV. Closer inspection of SET reveals that there is a significant spread in the size and duration of the SET included in those counts. Most notably, at higher VIN and LET a set of very large and long SET appears. Figure 3 shows a sampling of these large SET for VIN = 16.5V and LET = 60. The largest from this particular run was over +300mV from nominal and lasted well over 1ms. 0.9ms 100µs/DIV FIGURE 3. COMPOSITE (58) PLOT OF SELECTED LARGE AND LONG SET FOR ISL71091SEH33 AT LET = 60, VIN = 16.5V, IOUT = 1mA, COUT = 10µF Lowering the input voltage to VIN = 13.2V significantly suppressed the magnitude of the SET as can be noted in Figure 4. Thus the input voltage is a strong determiner of this large and long SET category. Submit Document Feedback 3 AN1938.0 June 4, 2014 Application Note 1938 100µs/DIV FIGURE 4. COMPOSITE (5) PLOT OF SELECTED LARGE AND LONG SET FOR ISL71091SEH33 AT LET = 60, VIN = 13.2V, IOUT = 1mA, COUT = 10µF It is also worth noting that reducing the output capacitor from 10µF to 0.1µF is effective in shortening the SET disturbance but is not effective in reducing the magnitudes. Comparing the magnitudes of Figure 5 with those of Figure 3 illustrates this point. In both figures, the peak prolonged SET is about +300mV, while in Figure 3 it persists over 1ms whereas in Figure 5 the SET is limited to within 200µs. Figures 3 through 7 indicate a strong dependence of SET magnitude on VIN and a strong dependence of the SET duration on COUT. Just as a confirmation, Figure 6 compared to Figure 3 demonstrates the impact of both VIN and COUT, although the peak magnitudes roughly double those of Figure 4. Finally, Figure 7 shows that the large and long SET are gone with a VIN = 5.5V at LET = 28. Only sharp spike SET remain (both positive and negative), with magnitudes larger than the slow events at COUT = 10µF. 100µs/DIV FIGURE 6. COMPOSITE (250) SET PLOT FOR ISL71091SEH33 AT LET = 60, VIN = 13.2V, IOUT = 1mA, COUT = 0.1µF 100µs/DIV FIGURE 7. COMPOSITE (250) SET PLOT FOR ISL71091SEH33 AT LET = 28 VIN = 5.5V, IOUT = 1mA, COUT = 0.1µF, CCOMP = 1nF. 100µs/DIV FIGURE 5. COMPOSITE (250) SET PLOT FOR ISL71091SEH33 AT LET = 60, VIN = 16.5V, IOUT = 1mA, COUT = 0.1µF Submit Document Feedback 4 AN1938.0 June 4, 2014 Application Note 1938 SET Testing of ISL71091SEH20, 2.048V Reference Four of the ISL71091SEH20 2.048 references were run to test for SET. A summary of the conditions and the SET counts obtained is in Table 3. TABLE 3. SET SUMMARY OF ISL71091SEH20 (2.048V) SAMPLES VIN PART A EVENTS (±20mV) PART B EVENTS (±20mV) NET CROSS SECTION (cm2) 1 16.5 416 663 1.1E-04 0.1 1 16.5 1787 1273 3.1E-04 60 1.0 1 13.2 449 549 1.0E-04 60 0.1 1 13.2 1671 1310 3.0E-04 60 1.0 1 5.5 316 467 7.8E-05 60 0.1 1 5.5 1391 2988 4.4E-04 28 1.0 1 16.5 102 148 2.5E-05 28 0.1 1 16.5 707 665 1.4E-04 28 1.0 1 13.2 68 133 2.0E-05 28 0.1 1 13.2 633 622 1.3E-04 28 1.0 1 11 38 138 1.8E-05 28 0.1 1 11 665 583 1.2E-04 28 1.0 1 5.5 41 42 8.3E-06 28 0.1 1 5.5 634 567 1.2E-04 8.5 1.0 1 16.5 0 1 1.0E-07 8.5 0.1 1 16.5 181 151 3.3E-05 8.5 1.0 1 13.2 0 0 -- 8.5 0.1 1 13.2 188 173 3.6E-05 8.5 1.0 1 5.5 2 1 3.0E-07 8.5 0.1 1 5.5 162 120 2.8E-05 (µF) CCOMP (nF) 60 1.0 60 LET COUT NOTE: 4. Trigger level for the output voltage set to ±20mV and IOUT = 1mA. Each irradiation was to 5x106 ion/cm2. SET for the ISL71091SEH20 varied considerably with the selection of COUT (either 0.1µF or 1µF) and the headroom voltage on VIN. Examples of the SET waveforms captured are shown in Figures 8 through 12. Submit Document Feedback 5 20µs/DIV FIGURE 8. COMPOSITE (100) PLOT OF SET FOR ISL71091SEH20 AT LET = 60 VIN = 16.5V, IOUT = 1mA, COUT = 0.1µF, CCOMP = 1nF. TRIGGER AT ±20mV, WHILE SCOPE TRUNCATES SET TRACES AT ±400mV. 20µs/DIV FIGURE 9. COMPOSITE PLOT OF 100 SET FOR ISL71091SEH20 AT LET = 60 VIN = 16.5V, IOUT = 1mA, COUT = 1µF, CCOMP = 1nF. TRIGGER AT ±20mV. Figures 8 and 9 show the SET resulting with VIN = 16.5V and LET = 60 MeV•cm2/mg. In the case of Figure 8 (COUT = 0.1µF) some SET exceeded 400mV deviation from the 2.048V regulation point, both positive and negative at IOUT = 1mA. In this case, the SET duration was about 30µs. For Figure 9 (COUT = 1µF) the SET deviations were limited to about +250mV and -100mV at IOUT = 1mA. However, the durations are much longer with some overshoot (undershoot) evident beyond 80µs. A few SET in Figure 9 are very long and extrapolate out to about 1ms, but this again is at VIN = 16.5V. These events represent a cross section of about 2x10-6 cm2. These very long SET are consistent with what was seen on the ISL71091SEH33 (3.3V) reference. It is interesting to note that these long SET disappeared with a reduced VIN = 13.2V as exhibited in Figure 10. Figure 11 is also free of these long SET for VIN = 5.5V, and a moderate reduction in SET peak deviations is also seen. LET = 28 MeV•cm2/gm is insufficient to generate AN1938.0 June 4, 2014 Application Note 1938 these long SET even with VIN = 16.5V, as shown in Figure 12 as compared to Figure 9. 20µs/DIV 20µs/DIV FIGURE 10. COMPOSITE (100) PLOT OF SET FOR ISL71091SEH20 AT LET = 60 VIN = 13.2V, IOUT = 1mA, COUT = 1µF, CCOMP = 1nF. TRIGGER AT ±20mV. FIGURE 12. COMPOSITE (100) PLOT OF SET FOR ISL71091SEH20 AT LET = 28 VIN = 16.5V, IOUT = 1mA, COUT = 1µF, CCOMP = 1nF. TRIGGER AT ±20mV. 20µs/DIV 20µs/DIV FIGURE 11. COMPOSITE (100) PLOT OF SET FOR ISL71091SEH20 AT LET 60 VIN = 5.5V, IOUT = 1mA, COUT = 1µF, CCOMP = 1nF. TRIGGER AT ±20mV. Submit Document Feedback 6 FIGURE 13. COMPOSITE PLOT OF 100 SET FOR ISL71091SEH20 at LET = 60, VIN = 5.5V, IOUT = 1mA, COUT = 0.1µF, CCOMP = 1nF. TRIGGER AT ±20mV AND SCOPE TRUNCATING SET AT ±400mV. Even at VIN = 5.5V the SET can exceed ±400mV with COUT = 0.1µF. Thus the SET performance is very much linked to both the selection of COUT and VIN. Comparing Figure 13 to Figure 11 shows that the magnitude of the SET are reduced from greater than 400mV with COUT = 0.1µF (Figure 13) to less than 125mV (Figure 11), but the duration grows from under 20µs to about 200µs. Comparing Figure 12 to Figure 11 indicates that the magnitude of the SET does not diminish much with the reduction in ion LET from 60 to 28 MeV•cm2/mg. AN1938.0 June 4, 2014 Application Note 1938 SET Testing of ISL71091SEH40, 4.096V Reference both maximum sink (-5mA) and source current (10mA) at LET 28 and 8.5 MeV•cm2/mg. SET captures were triggered at ±20mV deviation from DC. Four samples of the ISL71091SEH40 (4.096V reference) were tested for SET as summarized in Table 4. Parts were tested at TABLE 4. SUMMARY OF SET TESTING ON ISL71091SEH40 SET COUNTS (±20mV), 4e6 ion/cm2 COUT = 0.1µF CCOMP = 1nF COUT = 1µF CCOMP = 10nF DUT 1 DUT 2 DUT 3 DUT 4 6 1043 110 46 0 302 7.5 1042 66 36 0 303 30 1021 (Figure 14) 34 (Figure 16) 214 0 6 1270 50 60 0 305 7.5 1294 75 52 0 306 30 1144 33 (Figure 17) 193 (Figure 19) 0 6 162 0 0 0 202 7.5 175 0 0 0 203 30 208 0 0 0 6 139 0 0 0 205 7.5 157 1 0 0 206 30 204 2 (Figure 18) 0 0 Run LET MeV (mg/cm2) IOUT (mA) VIN (V) 301 28 -5 304 201 10 8.5 -5 204 10 COUT = 10µF CCOMP = 10nF NOTE: 5. Bold entries correspond to composite SET plot in Figures 14 through 18. There is a clear difference between DUT3 and DUT4 even though they had the same capacitance values. It was noted that the SET triggering on DUT3 were spikes of <10ns duration, (see Figure 20) so the difference was in registering these very short events. The oscilloscopes were swapped and the difference between DUT3 and DUT4 remained the same, so the difference was not the oscilloscope. Very likely the difference was due to a difference in the COUT impedance as dominated by PC board parasitics, but that is speculation. It is clear that the decrease in LET from 28 to 8.5 MeV•cm2/mg significantly reduced the number of SET reaching the ±20mV trigger threshold. Also, the selection of capacitor values had a strong influence on captures. At COUT = 1µF and CCOMP = 10nF SET reaching ±20mV were nearly eliminated for LET 8.5 MeV•cm2/mg. With COUT = 10µF, no SET at all of ±20mV were recorded. The SET counts for DUT1 runs 301 through 306 were very similar and the SET transients were of the form represented in Figure 14 which shows all the SET for run 303 and DUT1. A few large positive SET extended to a maximum of +520mV, and a single large negative SET reached 330mV. However, the vast majority of SET captured was within ±100mV. The major SET deviation was over in about 20µs with the tail extending about 100µs. These characteristics held for the other 300 series runs on DUT1. 50µs/DIV FIGURE 14. COMPOSITE PLOT OF 1021 SET FOR DUT1 RUN 303: COUT = 0.1µF, CCOMP = 1nF, IOUT = -5mA, VIN = 30V, LET = 28 A slightly different way to look at the SET is provided in Figure 15. It is clear in this view just how rare the larger SET’s are. Virtually Submit Document Feedback 7 AN1938.0 June 4, 2014 Application Note 1938 only two SET recorded on DUT2 for run 206 and these barely made the ±20mV trigger level. 3.0E-04 2.5E-04 2.0E-04 1.5E-04 1.0E-04 50µs/DIV 5.0E-05 0 6.75E-06 5.00E-07 -300 -275 -250 -225 -200 -175 -150 -125 -100 -75 -50 -25 0 25 50 75 100 125 150 175 200 225 250 275 300 325 350 375 400 425 450 CUMULATIVE CROSS SECTION FOR SET DEVIATION GREATER OR EQUAL TO BIN (cm2) all the positive SET are between -175mV and +25mV; only a 6.75x10-6 cross section represents larger positive events. There were 27 events above +250mV out of 1021 total captures. Negative SET are almost all smaller than 200mV. SET DEVIATION FROM DC (mV, 25mV BINS) FIGURE 17. COMPOSITE PLOT OF 33 SET FOR DUT2 RUN 306: COUT = 1µF, CCOMP = 10nF, IOUT = 10mA, VIN = 30V, LET = 28 FIGURE 15. SUMMARY OF RUN 301 DUT1 SET CROSS SECTIONS BY DEVIATION. THE COLUMNS REPRESENT THE CROSS SECTION OF SET WITH DEVIATIONS LARGER THAN THE BIN THE COLUMN IS IN. DUT2, with COUT = 1µF and CCOMP = 10nF, exhibited different SET characteristics from DUT1 as shown in Figure 16. The count of SET exceeding ±20mV is reduced by a factor of 30, and those captured were bounded by +75mV and -50mV and decayed in 100µs. Despite the higher SET counts for DUT2 on runs 301 and 302 the SET form was the same. 50µs/DIV FIGURE 18. COMPOSITE PLOT OF THE 2 SET FOR DUT2 RUN 206: COUT = 1µF, CCOMP = 10nF, IOUT = 10mA, VIN = 30V, LET = 8.5 50µs/DIV FIGURE 16. COMPOSITE PLOT OF 34 SET FOR DUT2 RUN 303: COUT = 1µF, CCOMP = 10nF, IOUT = -5mA, VIN = 30V, LET = 28 Finally, the SET for DUT3 (COUT = 10µF, CCOMP = 10nF) at LET = 28 MeV•cm2/mg are shown in Figure 19. It should be noted that the time scale in Figure 19 is marked 1x10-6 seconds where as the previous plots were in 1x10-5 seconds. The plots in Figure 19 do not reach the ±20mV triggering levels due to the plotting software routine (MATLAB), filtering out the triggering event, which was very short and sharp. An example of the direct oscilloscope capture for DUT3 in run 301 is shown in Figure 20. Here it can be seen that the event triggering the oscilloscope was only about 10ns wide and negative. Figure 17 shows the form of the SET shifted with a change in load current from -5mA to +10mA. In this case the negative SET extended down to -90mV, but the positive SET were essentially unchanged at about +75mV. When the LET was dropped to 8.5 MeV•cm2/mg the SET reaching ±20mV on DUT2 virtually vanished. Figure 18 shows the Submit Document Feedback 8 AN1938.0 June 4, 2014 Application Note 1938 TABLE 5. SUMMARY OF SET TESTING OF ISL71091SEH10 SAMPLES 1µs/DIV FIGURE 19. COMPOSITE PLOT OF THE 193 SET FOR DUT3 RUN 306: COUT = 10µF, CCOMP = 10nF, IOUT = 10mA, VIN = 30V, LET = 28 PART B EVENTS (±100mV) NET CROSS SECTION (cm2) 46 1.2E-05 LET COUT (µF) CCOMP (nF) VIN PART A EVENTS (±100mV) 60 1 1 16.5 74 60 0.1 1 16.5 60 1 1 13.2 60 0.1 1 13.2 28 1 1 16.5 0 0 -- 28 0.1 1 16.5 81 93 1.7E-05 28 1 1 13.2 0 0 -- 28 0.1 1 13.2 94 95 1.9E-05 8.5 1 1 16.5 0 0 -- 8.5 0.1 1 16.5 1 (257 Note 7) 2 (49 Note 7) 3.1E-05 8.5 1 1 13.2 0 0 -- 8.5 0.1 1 13.2 0 (234 Note 7) 0 (124 Note 7) -- 419 441 (2962 Note 7) (989 Note 7) 79 64 4.0E-04 1.4E-05 445 498 4.0E-04 (2992 Note 7) (1027 Note 7) NOTES: 6. The IOUT for each part was 1mA and the fluency for each irradiation was 5x106 ion/cm2. 7. Counts were captured with a ±20mV trigger. FIGURE 20. DIRECT OSCILLOSCOPE CAPTURE OF A DUT3 SET FROM RUN 301 SET Testing of ISL71091SEH10, 10.0V Reference Four ISL71091SEH10 (10.0V) parts were initially SET tested as outlined in Table 5. The counts of ±100mV (±1%) SET were highly sensitive to the value of COUT. Figure 21 shows the plot of cross sections versus LET. The cross section at LET = 60 was reduced by almost an order of magnitude in going from COUT = 0.1µF to COUT = 1µF. The ±20mV (0.2%) SET were much more common but were not captured for all cases and are not converted to cross sections here. Figures 22 and 23 provide comparison of the SET forms for the two different output capacitors, 0.1µF and 1µF. The SET with the smaller COUT value reach the oscilloscope clipping limits of ±400mV, but the SET for the larger COUT are maintained within ±200mV. However, the duration grows from 20µs to 100µs. There does not appear to be significant overshoot/undershoot in the case of COUT = 1µF that appears in case of the 2.048V reference. Figure 24 shows that SET of significant magnitude (>300mV) are induced by ions with LET of 8.5 MeV•cm2/mg. However, with COUT = 1µF all SET were suppressed to below the ±100mV triggering threshold for LET < 60. It appears that COUT = 1µF is sufficient to hold all 10V output SET within ±100mV for LET ≤ 28 MeV•cm2/mg and IOUT = 1mA. Both positive and negative SET’s are in evidence at the 1mA output current. At LET = 60, SET larger than 100mV do occur. Submit Document Feedback 9 AN1938.0 June 4, 2014 Application Note 1938 SET (±100mV) CROSS SECTION (cm2) 1.0E-04 9.0E-05 8.0E-05 0.1µF 13.2V 7.0E-05 0.1µF 16.5V 6.0E-05 5.0E-05 4.0E-05 1µF 13.2V 3.0E-05 2.0E-05 1.0E-05 1µF 16.5V 0.0E+00 0 10 20 30 40 50 60 20µs/DIV 70 ION LET (MeV·cm2/mg) FIGURE 21. PLOT OF NOMINAL CROSS SECTION FOR THE VARIOUS CONDITIONS TESTED FOR THE ISL71091SEH10 20µs/DIV FIGURE 22. COMPOSITE PLOT OF 100 SET FOR ISL71091SEH10 AT LET = 60, VIN = 16.5V, IOUT = 1mA, COUT = 0.1µF, CCOMP = 1nF. CAPTURE TRIGGER AT ±20mV, SCOPE TRUNCATED SET AT ±400mV. FIGURE 23. COMPOSITE (74) PLOT OF SET FOR ISL71091SEH10 AT LET = 60, VIN = 16.5V, IOUT = 1mA, COUT = 1µF, CCOMP = 1nF. CAPTURE TRIGGER AT ±100mV. 20µs/DIV FIGURE 24. COMPOSITE (49) PLOT OF SET FOR ISL71091SEH10 AT LET = 8.5, VIN = 16.5V, IOUT = 1mA, COUT = 0.1µF, CCOMP = 1nF. CAPTURE TRIGGER AT ±20mV Further SET testing was done on four additional parts of the ISL71091SEH10 to look at the lower LET and the impact of the capacitor selection. A summary of this testing is shown in Table 6. Submit Document Feedback 10 AN1938.0 June 4, 2014 Application Note 1938 TABLE 6. SUMMARY OF SECOND ROUND OF SET TESTING ON THE ISL71091SEH10 SET Counts (±20mV), 4e6 ion/cm2 COUT = 0.1µF CCOMP = 1nF COUT = 1µF CCOMP = 10nF COUT = 10µF CCOMP = 10nF DUT 1 DUT 2 DUT 3 DUT 4 Run LET IOUT (mA) VIN (V) 311 28 -5 6 1129 58 183 13 312 7.5 1103 67 196 34 313 30 952 (Figure 25) 38 (Figure 27) 435 (Figure 28) 62 6 1229 70 162 9 315 7.5 1379 73 211 28 316 30 1219 39 437 59 6 176 1 0 0 212 7.5 162 0 0 0 213 30 154 (Figure 26) 1 0 0 6 179 0 0 0 215 7.5 161 0 0 0 216 30 194 0 0 0 314 211 10 8.5 -5 214 10 NOTE: 8. Bold entries correspond to composite SET plot in Figures 25 through 28. Clearly the count of ±20mV SET is reduced considerably in going from COUT = 0.1µF and CCOMP = 1nF to COUT = 1µF and CCOMP = 10nF. The change going from COUT = 1µF to COUT = 10µF is less clear due to the discrepancy between DUT3 and DUT4. This difference mimics the difference between DUT3 and DUT4 of the 4.096V reference. Figure 25 displays the 952 events registered for run 313 on DUT1. The similarity of these SET with those observed for the 4.096V reference (Figure 14) is clear, even to the deviations of the SET. Reducing the LET to 8.5 MeV•cm2/mg reduces the SET magnitudes as well as the ±20mV SET counts (952 to 154) as shown in Figure 26. Clearly the LET determines the magnitude of the resulting SET. Although one SET reached +270mV and one reached -75mV, the rest of the SET were bounded by +100mV and -50mV. The impact of changing COUT to 1µF and CCOMP to 10nF is apparent in Figure 27 (run 313 DUT2). Not only has the SET count dropped from 952 to 38, but the extremes of the SET have dropped to +75mV and -60mV. This is virtually identical to the case of the 4.096V reference depicted in Figure 16. 50µs/DIV FIGURE 25. COMPOSITE PLOT OF 952 SET FROM RUN 313 ON DUT1: COUT = 0.1µF, CCOMP = 1nF, IOUT = 10mV, VIN = 30V, LET = 28 For the case of COUT = 10µF and CCOMP = 10nF the 10V reference again correlates with the 4.096V reference in that SET under 5mV register on the plotting diagrams. Submit Document Feedback 11 AN1938.0 June 4, 2014 Application Note 1938 50µs/DIV 50µs/DIV FIGURE 26. COMPOSITE PLOT OF 154 SET FROM RUN 213 DUT1: COUT = 0.1µF, CCOMP = 1nF, IOUT = -5mA, VIN = 30V, LET = 8.5. FIGURE 28. COMPOSITE PLOT OF 435 SET FROM RUN 313 DUT3: COUT = 10µF, CCOMP = 10nF, IOUT = -5mA, VIN = 30V, LET = 28 Conclusions SEE testing of the ISL71091SEH precision reference product family has demonstrated that the devices are immune to SEB and SEL to an LET of 86.4 MeV•cm2/mg with an input voltage up to 36V and a load current of either -5mA or +10mA. This represents a supply voltage 20% over the recommended maximum operation of 30V and at the limits of the recommended output drive current capability. Although SEB/SEL (destructive ion testing) was only done on the 3.3V version (ISL71091SEH33) these results apply to all of the ISL71091SEHxx family since they share the same silicon design. 50µs/DIV FIGURE 27. COMPOSITE PLOT OF 38 SET FROM RUN 313 DUT2: COUT = 1µF, CCOMP = 10nF, IOUT = -5mA, VIN = 30V, LET = 28. SET testing demonstrated that a larger COUT serves to suppress the SET deviation magnitude but brings some jeopardy. A COUT = 10µF was very effective in limiting SET at LET = 28 MeV•cm2/mg as can be best seen in the results for the 4.096V and 10.0V references. However, at LET = 60 MeV•cm2/mg and VIN = 16.5V on the 3.3V and 2.048V references a large and long SET form appeared (Figures 3 and 9). This implies a compromise with capacitor selection and SET performance. If large and short (±500mV and 25µs) SET in response to relatively low LET (28 MeV•cm2/mg) can be tolerated, the minimal capacitance values of COUT = 0.1µF and CCOMP = 1nF can be used. However, if suppression of these common events is needed, going to COUT = 10µF and CCOMP = 10nF virtually eliminates the SET but opens up the potential for rarer events at higher LET and VIN (>13.2V), which are large (several hundred millivolts) and long (~1ms). There is not a clear “best” choice of capacitance values as every choice brings with it an SET consequence. The user is encouraged to carefully review the data presented in the report in considering and deciding upon the VIN, COUT, and CCOMP values to be used in an application. Intersil Corporation reserves the right to make changes in circuit design, software and/or specifications at any time without notice. Accordingly, the reader is cautioned to verify that the Application Note or Technical Brief is current before proceeding. For information regarding Intersil Corporation and its products, see www.intersil.com Submit Document Feedback 12 AN1938.0 June 4, 2014