ISL75052SEH SEE Test Report

Application Note 1851
Single-Event Performance of the ISL75052SEH
Introduction
Part Description
The intense proton and heavy ion environment encountered in
space applications can cause a variety of Single-Event Effects
(SEE) in electronic circuitry, including Single-Event Upset (SEU),
Single-Event Transient (SET), Single-Event Functional Interrupt
(SEFI), Single-Event Latch-up (SEL), Single-Event Burnout (SEB)
and Single-Event Gate Rupture (SEGR). 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.
The ISL75052SEH is a radiation hardened, single output LDO
specified for a maximum output current of 1.5A. The device is
specified to operate from input voltages over the 4.0V to 13.2V
range. Attainable output voltages are bounded by a 0.6V
reference on the low end and a 225mV dropout at 1.5A or
75mV at 0.5A. The output is adjustable based on an external
resistor divider. The 16-lead dual in-line ceramic flatpack has a
metal pad on the bottom to facilitate thermal management.
The part has an enable input (EN) and an open-drain
power-good (PG) signal.
This report discusses the results of Intersil’s SEE testing of the
ISL75052SEH LDO. Testing was carried out with two objectives
in mind. The first was to establish safe operating limits with
regard to input voltage and incident ion linear energy transport
(LET). The second was to establish the characteristics of SET
under normal operating conditions.
Irradiation Test Facility
Note: Throughout this document LETEFF is used to indicate
effective linear energy transfer in units of MeV*cm2/mg. For
brevity the units are omitted and should be understood
throughout the rest of the document.
Executive Summary of Results
Damaging SEE (SEB, SEGR, or SEL)
No damage was recorded for parts tested at VIN ≤15.0V,
LETEFF = 86 (Au at normal incidence), and case temperature
at +125°C ±10°C. Parts were tested both disabled (i.e.
VOUT = 0.0V) and with VOUT = 14.0V and IOUT = 1.8A.
Testing was performed at the Radiation Effects Facility of
Texas A&M University’s (TAMU) Cyclotron Institute in College
Station, Texas. The TAMU facility is coupled to a K500
super-conducting cyclotron, which is capable of generating a
wide range of ion species with the various energy, flux and
fluence levels needed for SEE testing. Details about the facility
and the ion beams can be found on the TAMU Cyclotron
Institute web site (http://cyclotron.tamu.edu/ref/). The testing
reported here was done March 7, 2013.
Reference Documents
• ISL75052SEH Datasheet
• ISL75052SEH Evaluation Board User Guide
• ISL75052SEH Radiation Test Report
• SMD (5962-13220)
Single-Event Functional Interrupt (SEFI)
No SEFI were observed during any of the testing, and no SET on
power-good (PG) to a 0.5V trigger was captured either.
Single-Event Transient (SET)
No VOUT SETs were observed in excess of a VOUT deviation
window of +35mV and -20mV.
No power-good (PG) SET were found for an observational
threshold of 0.5V.
The output capacitance was composed of two tantalum
capacitors (T541X107M025AH6510) with nominal values of
100µF and 60mΩ ESR.
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Application Note 1851
FIGURE 1. SCHEMATIC USED FOR SEE TESTING
SEE Testing Description
SEE testing was carried out with samples mounted on the
engineering evaluation boards. Loading was provided by an
electronic load. The schematic of the board is shown in Figure 1.
Digital multimeters monitored input voltage (VIN), output voltage
(VOUT) and input current (IIN). In disabled test cases the leakage
current to the output (ILK) was monitored. For damaging SEE
(SEB, SEGR, SEL) studies the parts were heated with a film
heater on the back of the circuit board to +125°C ±10°C case
temperature. The heater current to achieve the desired case
temperature was determined prior to the TAMU trip and applied
during testing. Parameters VOUT, IIN and ILK were monitored
before and after irradiation as indications of part damage. For
the SET studies the case temperature was left to ambient. VOUT
and PG (power-good) were used as the triggering signal for a
LeCroy wave Runner 4-channel digital oscilloscope to capture
SET. Other channels that were simultaneously captured the
reference voltage (BYP), and the parts internally generated low
voltage supply (VCCX).
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Damaging SEE Testing and Results (SEB,
SEGR, SEL)
The test matrix run for damaging SEE on the ISL75052 appears
in Table 1. The same four parts (device under test, DUT) were
used for all the testing and accumulated about 55krad(Si) by the
end of the testing. The parameters monitored pre and post
irradiation to look for damage are listed with the actual
measurements. The measurement variations are all within the
on-site measurement repeatability so there is no evidence of
damage. VIN = 14.7V was the intended goal for passing SEE
without damage, while the VIN = 15.0V was an effort to
document some margin against that goal.
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TABLE 1. DAMAGING SEE TESTING MATRIX
UNIT
VIN
(V)
IOUT
(A)
PRE
DUT1
14.7
14.7
DUT2
1.8
14.011
1.8
14.011
DUT3
1.8
13.978
1.8
13.980
DUT4
1.8
13.973
1.8
13.969
13.969
Disabled
1.8
14.040
15.0
15.0
13.975
Disabled
14.7
14.7
13.979
Disabled
15.0
15.0
13.980
Disabled
14.7
14.7
14.012
Disabled
15.0
15.0
14.012
Disabled
14.7
14.7
POST
Disabled
15.0
15.0
IIN
(mA)
IOUT = 0
VOUT
(V)
14.040
Disabled
1.8
14.051
14.051
ILK
(nA)
VOUT = 0
PRE
POST
PRE
POST
9.5
9.5
200
200
24.8
24.6
9.7
9.8
270
255
24.7
24.8
9.5
9.5
260
260
24.1
24.2
9.7
9.8
290
280
24.4
24.3
9.5
9.5
260
260
23.9
23.7
9.7
9.8
325
332
24.2
24.1
9.5
9.5
330
330
24.0
24.0
9.7
9.7
365
350
24.3
24.1
NOTE: Each of the 16 tests listed was done with Au at 0° (LETEFF = 86), TC = +125°C, and flux of 5x104 ion*cm-2*s-1 to fluence of 1x107 ion/cm2.
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Application Note 1851
Damaging SEE (SEB, SEGR, SEL) Discussion
Conservatively the data in Table 1 represents a fluence of 8x107
ion/cm2 at VIN 14.7V and LETEFF = 86 without a failure. This
corresponds to a nominal cross section of 1.25x10-8 cm2, which
is smaller than any active device in the product and so is a very
strong statement against damage susceptibility at LETEFF = 86.
The clean results at VIN = 15.0V provide evidence of extra margin
against the 14.7V product claim for SEB, SEGR, and SEL free
operation.
SET Testing and Results
SET testing was done with gold (Au) at zero degrees incidence for
LETEFF = 86. The device temperature was left to the ambient
conditions. The output voltage (VOUT) was set to 3.5V for all tests.
Four units were tested with irradiation runs at each of three
different conditions: VIN = 4.0V and IOUT = 0.1A, VIN = 4.0V and
IOUT = 1.5A, and VIN = 13.2V and IOUT = 0.1A. The first two
conditions cover a load range for low supply headroom (0.5V
between VIN and VOUT) and the last condition looks at high
supply headroom (9.7V). In the last case, the current was only
tested at 0.1A because of thermal considerations. It was
anticipated that the high load current and low headroom
condition (nearest drop-out) would be the worst case for negative
transients, and the low load current and high headroom case
would be the worst for positive transients. This was indeed found
to be the case.
Oscilloscope triggering on VOUT was set to capture transients
with ±10mV VOUT deviations and also ±75mV VOUT deviations.
The BYP and VCCX were also captured on any VOUT trigger for
information on the origin of the SET. The captures were set to
start 20µs prior to the trigger and end 80µs after the trigger.
No SETs were captured with the ±75mV trigger during 1x107
ion/cm2 of each run. The ±10mV transients were plentiful;
capturing was terminated at roughly 200 SET captures for each
run. The 200 SET count limit was reached at about 2x106
Composite Plots
VOUT (ordinate) is 10mV/div.
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No SET on PG (power-good, to a -0.5V trigger) was registered.
TABLE 2. SUMMARY OF VOUT SET TESTING
COUNT
TERMINATING
FLUENCE
201
1.92E+06
200
1.88E+06
202
1.96E+06
202
2.02E+06
202
1.22E+06
202
1.18E+06
206
8.66E+05
4
272
1.54E+06
423
1
201
2.22E+06
426
2
202
1.89E+06
429
3
202
1.90E+06
432
4
202
1.52E+06
RUN
DUT
421
1
424
2
427
3
430
4
422
1
425
2
428
3
431
VIN
IOUT
0.1
4.0
1.5
13.2
0.1
SET Composite Plots and Discussion
The following plots give a qualitative look at the SET populations
captured. For each of the three operating conditions tests has a
plot for each of the four DUTs. These plots are composites of the
first 200.
All SET captured for each DUT at VIN = 4.0V, VOUT = 3.5V, IOUT = 0.1A. Time (abscissa) is 10µs/div and
FIGURE 2. DUT1
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ion/cm2 for IOUT = 0.1A, but was reached at about 1.3x106
ion/cm2 for the 1.5A load. This reflects the generation of
negative transients achieving the trigger value with the higher
load current (1.5A); the same SET at the lower load current (0.1A)
did not reach the trigger value and so were not captured.
FIGURE 3. DUT2
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Composite Plots
All SET captured for each DUT at VIN = 4.0V, VOUT = 3.5V, IOUT = 0.1A. Time (abscissa) is 10µs/div and
VOUT (ordinate) is 10mV/div. (Continued)
FIGURE 4. DUT3
FIGURE 5. DUT4
The vast majority of the SET for VIN = 4.0V and IOUT = 0.1A are
fast, positive transients indicating a rapid increase in the current
being supplied by the ISL75052SEH beyond the load demand
(0.1A). The fast, positive transients peak about 2µs to 3µs after
they start with a small spike at the top. The small spike at top of
the SET is due to the excess current encountering the high
frequency impedance of COUT. The falling edge of this spike
indicates the real SET is over in less than 5µs. However, COUT has
been overcharged in that time so that VOUT is now above the
setting. Since the ISL75052 has no active pull-down device, the
excess VOUT can only decay away through the load and feedback
divider. The 0.1A load and the COUT value then set the rate of
decay of the VOUT overvoltage (200µF at 0.1A for 0.5mV/µs or
5mV/div in the figures).
The few slow, negative transients begin with the characteristic
discharge rate of COUT indicating the part has stopped supplying
current. A bottom VOUT is reached above -20mV at which time
the parts supply of current resumes. A relatively slow (100s of
µs) recovery back to the nominal VOUT ensues. These slow,
negative VOUT transients correlated to small drops in the
reference voltage (BYP) used for regulation. The entire VOUT SET
can then be understood on the basis of a slight dropping of BYP
due to the ion. For the -20mV events seen here at VOUT = 3.5V,
the driving SET deviation in BYP is only about -3mV.
All the captured transients in Figures 6 through 9 are bounded by
a window of +25mV and -20mV deviation. These correspond
to+1% and -0.6% of the 3.5V output. At lower output voltages the
absolute magnitudes would be expected to apply; for a 1V output
the relative deviations would become +3.5% and -2%.
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Composite Plots
100 SET captured for each of DUTs 1 through 4 at VIN = 4.0V, VOUT = 3.5V, IOUT = 1.5A. Time (abscissa)
is 10µs/div and VOUT (ordinate) is 10mV/div.
FIGURE 6. DUT1
FIGURE 7. DUT2
FIGURE 8. DUT3
FIGURE 9. DUT4
With 1.5A of load current, the dominant form of SET captured
switched to a fast, negative transient. The high loading draws
VOUT down rapidly now when the device current being supplied is
interrupted. At the lower load (0.1A) the same SET would not
have resulted in a VOUT drop large enough to reach the 10mV
trigger. So it is not that any new SET form has appeared, it is just
that the SET are amplified by the higher load to the point of
capture. The fast, negative transient have a duration of only a few
microseconds (the precipitous fall in VOUT set by the load
current). Then the loop control recovers VOUT in about 20µs.
that similar BYP events would look significantly different from
those in Figures 10 through 13 other than a more rapid decline
followed by the same slow recovery.
These captured transients for IOUT = 1.5A are bounded by
+15mV and -20mV. This is less in both directions than the
previous case.
There are still some fast, positive transients. These are actually
the same transients seen in Figures 10 through 13, but the
higher load demand has modified the captured forms a bit. The
rise is not quite as fast and the spike at the top is gone. This is an
indication that the charging of COUT is much reduced; this is also
supported by the lower VOUT ramp starts.
There were no slow, negative transients observed. There is no
obvious reason for this to be the case. However, given the
correlation to the BYP disturbances, there is no reason to believe
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Composite Plots
200 SET captured for each of DUTs 1 through 4 at VIN = 13.2V, VOUT = 3.5V, IOUT = 0.1A. Time
(abscissa) is 10µs/div and VOUT (ordinate) is 10mV/div.
FIGURE 10. DUT1
FIGURE 11. DUT2
FIGURE 12. DUT3
FIGURE 13. DUT4
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Application Note 1851
For the case of VIN = 13.2V and IOUT = 0.1A the fast, positive
transients again dominate as they did in Figures 2 through 5
(VIN = 4.0V, IOUT = 0.1A). However, with more VIN headroom
(9.7V above VOUT) both the spike at the top of the SET and the
residual charging of COUT are larger. This indicates that more
current is being pushed during the SET. Clearly the worst case
positive SET are found for low load currents and high headroom
on VIN.
There is still one slow, negative transient that correlates to a
minuscule drop in BYP.
Under these conditions the transients are bounded by +35mV
and -15mV. Over all three operational conditions the observed
transients are bounded by a +35mV and -20mV window.
Further SET Discussion
No SEFIs, PG SETs, or VOUT SETs in excess of ±75mV were
observed to the full 1x107 ion/cm2 in each of the 12 SET runs
(4 DUTs, 3 conditions). This puts rather comfortable bounds on
any possible cross section for events. At the very least, 4x107
ion/cm2 failed to generate these events for each of the three
operating conditions. Taken together, a fluence of 1.2x108
ion/cm2 yielded no events.
A MATLAB program was applied to the SET data to extract the
peak deviation and the time duration outside the ±10mV
deviation window. The deviations were calculated based on the
VOUT of that trace prior to triggering, so there is a small offset
from the absolute scales of the SET plots. The results are plotted
in Figure 14. This clearly shows a SET deviation window (+33mV,
-20mV) and highlights two types of SET. Most SETs are a short
disturbance followed by a recovery time that depends on the
loading conditions. At light loading (0.1A) the positive SET are
larger and require time to discharge COUT. At high loading (1.5A)
negative SET dominate due to interruption in current, and the
recovery proceeds immediately after that SET when control loop
reasserts itself and supplies recovery current. The long negative
SET are due to small drops in the reference voltage and require a
longer time to recover.
FIGURE 14. SET DURATION VERSUS SET PEAK DEVIATION FOR ALL
CAPTURED DATA
Another way to look at the SET population is to consider the cross
section presented by the various SET magnitudes. This approach
yields the plot in Figure 15. The small population of long,
negative SET so obvious in Figure 14 corresponds to the very
small cross section negative events in Figure 15.
FIGURE 15. SET REPRESENTED AS CROSS SECTION BY EVENT VOUT
PEAK DEVIATION
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