IEC 62396-1:2012

IEC 62396-1 ®
Edition 1.0 2012-05
INTERNATIONAL
STANDARD
colour
inside
Process management for avionics – Atmospheric radiation effects –
Part 1: Accommodation of atmospheric radiation effects via single event effects
within avionics electronic equipment

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IEC 62396-1 ®
Edition 1.0 2012-05
INTERNATIONAL
STANDARD
colour
inside
Process management for avionics – Atmospheric radiation effects –

Part 1: Accommodation of atmospheric radiation effects via single event effects

within avionics electronic equipment

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
XD
ICS 03.100.50; 31.020; 49.060 ISBN 978-2-83220-099-5

– 2 – 62396-1  IEC:2012(E)
CONTENTS
FOREWORD . 5
INTRODUCTION . 7
1 Scope . 8
2 Normative references . 8
3 Terms and definitions . 9
4 Abbreviations and acronyms . 16
5 Radiation environment of the atmosphere . 18
5.1 Radiation generation . 18
5.2 Effect of secondary particles on avionics . 18
5.3 Atmospheric neutrons . 18
5.3.1 General . 18
5.3.2 Energy spectrum of atmospheric neutrons . 19
5.3.3 Altitude variation of atmospheric neutrons . 20
5.3.4 Latitude variation of atmospheric neutrons . 21
5.3.5 Thermal neutrons within aircraft . 23
5.4 Secondary protons . 23
5.5 Other particles . 24
5.6 Solar enhancements . 25
5.7 High altitudes greater than 60 000 feet (18 290 m) . 25
6 Effects of atmospheric radiation on avionics . 26
6.1 Types of radiation effects . 26
6.2 Single event effects (SEE) . 26
6.2.1 General . 26
6.2.2 Single event upset (SEU) . 27
6.2.3 Multiple bit upset (MBU) and multiple cell upset (MCU) . 27
6.2.4 Single effect transients (SET) . 29
6.2.5 Single event latch-up (SEL) . 29
6.2.6 Single event functional interrupt (SEFI) . 30
6.2.7 Single event burnout (SEB) . 30
6.2.8 Single event gate rupture (SEGR) . 30
6.2.9 Single event induced hard error (SHE) . 31
6.2.10 SEE potential risks based on future technology . 31
6.3 Total ionising dose (TID) . 31
6.4 Displacement damage . 32
7 Guidance for system designs . 33
7.1 Overview . 33
7.2 System design . 36
7.3 Hardware considerations . 37
7.4 Parts characterisation and control . 38
7.4.1 Rigour and discipline . 38
7.4.2 Level A systems . 38
7.4.3 Level B . 39
7.4.4 Level C . 39
7.4.5 Levels D and E . 40
8 Determination of avionics single event effects rates . 40

62396-1  IEC:2012(E) – 3 –
8.1 Main single event effects . 40
8.2 Single event effects with lower event rates . 40
8.2.1 Single event burnout (SEB) and single event gate rupture (SEGR) . 40
8.2.2 Single event transient (SET) . 41
8.2.3 Single event hard error (SHE) . 41
8.2.4 Single event latch-up (SEL) . 41
8.3 Single event effects with higher event rates – Single event upset data . 42
8.3.1 General . 42
8.3.2 SEU cross-section . 42
8.3.3 Proton and neutron beams for measuring SEU cross-sections . 42
8.3.4 SEU per bit cross-section trends in SRAMs . 46
8.3.5 SEU per bit cross-section trends and other SEE in DRAMs . 47
8.4 Calculating SEE rates in avionics . 49
8.5 Calculation of availability of full redundancy . 50
8.5.1 General . 50
8.5.2 SEU with mitigation and SET . 50
8.5.3 Firm errors and faults . 51
9 Considerations for SEE compliance . 51
9.1 Compliance . 51
9.2 Confirm the radiation environment for the avionics application . 51
9.3 Identify system development assurance level . 51
9.4 Assess preliminary electronic equipment design for SEE . 51
9.4.1 Identify SEE-sensitive electronic components . 51
9.4.2 Quantify SEE rates . 51
9.5 Verify that the system development assurance level requirements are met for
SEE. 51
9.5.1 Combine SEE rates for entire system . 51
9.5.2 Management of parts control and dependability . 52
9.6 Corrective actions . 52
Annex A (informative) Thermal neutron assessment . 53
Annex B (informative) Methods of calculating SEE rates in avionics electronics . 54
Annex C (informative) Review of test facility availability . 60
Annex D (informative) Tabular description of variation of atmospheric neutron flux with
altitude and latitude . 68
Annex E (informative) Consideration of effects at higher altitudes . 69
Annex F (informative) Prediction of SEE rates for ions . 74
Annex G (informative) Late news as of 2011 on SEE cross-sections applicable to the
atmospheric neutron environment . 77
Bibliography . 88

Figure 1 – Energy spectrum of atmospheric neutrons at 40 000 feet (12 160 m),
latitude 45 degrees . 19
Figure 2 – Model of the atmospheric neutron flux variation with altitude (see Annex D) . 21
Figure 3 – Distribution of vertical rigidity cut-offs around the world . 22
Figure 4 – Model of atmospheric neutron flux variation with latitude . 22
Figure 5 – Energy spectrum of protons within the atmosphere . 24
Figure 6 – System safety assessment process . 34
Figure 7 – SEE in relation to system and LRU effect . 36

– 4 – 62396-1  IEC:2012(E)
Figure 8 – Variation of RAM SEU cross-section as function of neutron/proton energy . 44
Figure 9 – Neutron and proton SEU bit cross-section data . 45
Figure 10 – SEU cross-section in SRAMs as function of manufacture date . 47
Figure 11 – SEU cross-section in DRAMs as function of manufacture date . 48
Figure E.1 – Integral linear energy transfer spectra in silicon at 100 000 feet
(30 480 m) for cut-off rigidities (R) from 0 GV to 17 GV . 70
Figure E.2 – Integral linear energy transfer spectra in silicon at 75 000 feet (22 860 m)
for cut-off rigidities (R) from 0 to 17 GV . 70
Figure E.3 – Integral linear energy transfer spectra in silicon at 55 000 feet (16 760 m)
for cut-off rigidities (R) from 0 GV to 17 GV . 71
Figure E.4 – The influence of solar modulation on integral linear energy transfer
spectra in silicon at 150 000 feet (45 720 m) for cut-off rigidities (R) of 0 GV and 8 GV . 71
Figure E.5 – The influence of solar modulation on integral linear energy transfer
spectra in silicon at 55 000 feet (16 760 m) for cut-off rigidities (R) of 0 GV and 8 GV . 72
Figure E.6 – Calculated contributions from neutrons, protons and heavy ions to the
SEU rates of the Hitachi-A 4Mbit SRAM as a function of altitude at a cut-off –rigidity
(R) of 0 GV. 73
Figure E.7 – Calculated contributions from neutrons, protons and heavy ions to the
SEU rates of the Hitachi-A 4Mbit SRAM as a function of altitude  at a cut-off rigidity
(R) of 8 GV. 73
Figure F.1 – Example differential LET spectrum . 75
Figure F.2 – Example integral chord length distribution for isotropic particle
environment . 75
Figure G.1 – Variation of the high energy neutron SEU cross-section per bit as a
function of device feature size for SRAMs and SRAM arrays in microprocessors and
FPGAs . 79
Figure G.2 – Variation of the high energy neutron SEU cross-section per bit as a
function of device feature size for DRAMs . 80
Figure G.3 – Variation of the high energy neutron SEU cross-section per device as a
function of device feature size for NOR and NAND type flash memories . 81
Figure G.4 – Variation of the MCU/SBU percentage as a function of feature size based
on data from many researchers in SRAMs [43, 45]. 82
Figure G.5 – Variation of the high energy neutron SEFI cross-section in DRAMs as a
function of device feature size . 83
Figure G.6 – Variation of the high energy neutron SEFI cross-section in
microprocessors and FPGAs as a function of device feature size . 84
Figure G.7 – Variation of the high energy neutron single event latch-up (SEL) cross-
section in CMOS devices (SRAMs, processors) as a function of device feature size . 85
Figure G.8 – Single event burnout (SEB) cross-section in power devices (400 V –
1 200 V)as a function of drain-source voltage (V ) . 86
DS
Table 1 – Nomenclature cross reference . 35
Table B.1 – Sources of high energy proton or neutron SEU cross-section data . 55
Table B.2 – Some models for the use of heavy ion SEE data to calculate proton SEE
data . 56
Table D.1 – Variation of 1 MeV to 10 MeV neutron flux in the atmosphere with altitude . 68
Table D.2 – Variation of 1 MeV to 10 MeV neutron flux in the atmosphere with latitude . 68
Table G.1 – Information relevant to neutron-induced SET . 86

62396-1  IEC:2012(E) – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
PROCESS MANAGEMENT FOR AVIONICS –
ATMOSPHERIC RADIATION EFFECTS –

Part 1: Accommodation of atmospheric radiation effects via
single event effects within avionics electronic equipment

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
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2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
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3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
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5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
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6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
IEC 62396-1 has been prepared by IEC technical committee 107: Process management for
avionics.
IEC 62396-1 cancels and replaces IEC/TS 62396-1 published in 2006.
This International Standard includes the following technical changes with respect to the
Technical Specification:
a) Guidance has been provided on the environment for altitudes above 60 000 feet (18,3 km)
and the effects on electronics are documented in Annex E and F;
b) Annex G has been added to provide late news as of 2011 on SEE cross-sections
applicable to the atmospheric neutron environment.

– 6 – 62396-1  IEC:2012(E)
The text of this international standard is based on the following documents:
FDIS Report on voting
107/176/FDIS 107/182/RVD
Full information on the voting for the approval of this international standard can be found in
the report on voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all the parts in the IEC 62396 series, published under the general title Process
management for avionics – Atmospheric radiation effects, can be found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.

IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
62396-1  IEC:2012(E) – 7 –
INTRODUCTION
This industry-wide technical specification informs avionics systems designers, electronic
equipment, component manufacturers and their customers of the kind of ionising radiation
environment that their devices will be subjected to in aircraft, the potential effects this
radiation environment can have on those devices, and some general approaches for dealing
with these effects.
The same atmospheric radiation (neutrons and protons) that is responsible for the radiation
exposure that crew and passengers acquire while flying is also responsible for causing the
single event effects (SEE) in the avionics electronic equipment. There has been much work
carried out over the last few years related to the radiation exposure of aircraft passengers and
crew. A standardised industry approach on the effect of the atmospheric neutrons on
electronics should be viewed as consistent with and an extension of the on-going activities
related to the radiation exposure of aircraft passengers and crew.
Atmospheric radiation effects are one factor that could contribute to equipment hard and soft
fault rates. From a system safety perspective, using derived fault rate values, the existing
methodology described in ARP4754 (accommodation of hard and soft fault rates in general)
will also accommodate atmospheric radiation effect rates.
In addition, this International Standard refers to the JEDEC Standard JESD89A, which relates
to soft errors in electronics by atmospheric radiation at ground level (at altitudes less than
10 000 feet (3 040 m)).
– 8 – 62396-1  IEC:2012(E)
PROCESS MANAGEMENT FOR AVIONICS –
ATMOSPHERIC RADIATION EFFECTS –

Part 1: Accommodation of atmospheric radiation effects via
single event effects within avionics electronic equipment

1 Scope
This part of IEC 62396 is intended to provide guidance on atmospheric radiation effects on
avionics electronics used in aircraft operating at altitudes up to 60 000 feet (18,3 km). It
defines the radiation environment, the effects of that environment on electronics and provides
design considerations for the accommodation of those effects within avionics systems.
This International Standard is intended to help aerospace equipment manufacturers and
designers to standardise their approach to single event effects in avionics by providing
guidance, leading to a standard methodology.
Details of the radiation environment are provided together with identification of potential
problems caused as a result of the atmospheric radiation received. Appropriate methods are
given for quantifying single event effect (SEE) rates in electronic components. The overall
system safety methodology should be expanded to accommodate the single event effects
rates and to demonstrate the suitability of the electronics for the application at the component
and system level.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC/TS 62239:2008, Process management for avionics – Preparation of an electronic
components management plan
NOTE IEC/TS 62239-1, Process management for avionics – Management plan – Part 1: Preparation and
maintenance of an electronic components management plan is under study and will supersede IEC/TS 62239.
IEC/TS 62396-2:2008, Process management for avionics – Atmospheric radiation effects –
Part 2: Guidelines for single event effects testing for avionics systems
IEC/TS 62396-3, Process management for avionics – Atmospheric radiation effects – Part 3:
Optimising system design to accommodate the single event effects (SEE) of atmospheric
radiation
IEC/TS 62396-4:2008, Process management for avionics – Atmospheric radiation effects –
Part 4: Guidelines for designing with high voltage aircraft electronics and potential single
event effects
IEC/TS 62396-5, Process management for avionics – Atmospheric radiation effects – Part 5:
Guidelines for assessing thermal neutron fluxes and effects in avionics systems

62396-1  IEC:2012(E) – 9 –
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
NOTE Users of this international standard may use alternative definitions consistent with convention within their
companies.
3.1
aerospace recommended practice
documents relating to avionics which are published by the Society of Automotive Engineers
(SAE)
3.2
analogue single event transient
ASET
spurious signal or voltage produced at the output of an analogue device by the deposition of
charge by a single particle
3.3
availability
probability that a system is working at instant t, regardless of the number of times it may have
previously failed and been repaired
Note 1 to entry: For equipment, the fraction of time the equipment is functional divided by the total time the
equipment is expected to be operational, i.e. the time the equipment is functional plus any repair time.
3.4
avionics equipment environment
for aeronautical equipment, the applicable environmental conditions (as described per the
equipment specification) that the equipment is able to withstand without loss or degradation
in equipment performance during all of its manufacturing cycle and maintenance life
Note 1 to entry: The length of the maintenance life is defined by the equipment manufacturer in conjunction with
customers.
3.5
capable
ability of a component to be used successfully in the intended application
3.6
certified
assessment and compliance to an applicable third party standard and maintenance of a
certificate and registration (i.e. JAN, IECQ)
3.7
characterisation
process of testing a sample of components to determine the key electrical parameter values
that can be expected of all produced components of the type tested
3.8
component application
process that assures that the component meets the design requirements of the equipment in
which it is used
3.9
component manufacturer
organisation responsible for the component specification and its production

– 10 – 62396-1  IEC:2012(E)
3.10
critical charge
smallest charge that will cause a SEE if injected or deposited in the sensitive volume
Note 1 to entry: For many devices, the unit applied was the picocoulomb (pC); however, for small geometry
devices, this parameter is measured in femtocoulomb (fC).
3.11
cross-section
σ
in radiation terms for proton and neutron interactions, combination of sensitive area and
probability of an interaction depositing the critical charge for a SEE
Note 1 to entry: The cross-section may be calculated using the following formula:
σ = number of errors/particle fluence
Note 2 to entry: The units for cross-section are cm per device or per bit.
3.12
digital single event transient
DSET
spurious digital signal or voltage, induced by the deposition of charge by a single particle that
can propagate through the circuit path during one clock cycle
Note 1 to entry: See 6.2.4 of this document.
3.13
electron
elementary particle having a mass of approximately 1/1 840 atomic mass units, and negative
–19
charge of 1,602 × 10 C
3.14
electronic components management plan
ECMP
equipment manufacturer's document that defines the processes and practices for applying
components to an equipment or range of equipment
Note 1 to entry: Generally, it addresses all relevant aspects of controlling components during system design,
development, production, and post-production support.
3.15
electronic components
electrical or electronic devices that are not subject to disassembly without destruction or
impairment of design use
Note 1 to entry: They are sometimes called electronic parts, or piece parts.
EXAMPLE Resistors, capacitors, diodes, integrated circuits, hybrids, application specific integrated circuits,
wound components and relays.
3.16
electronic equipment
item produced by the equipment manufacturer, which incorporates electronic components
EXAMPLE End items, sub-assemblies, line-replaceable units and shop-replaceable units.
3.17
electronic flight instrumentation system
EFIS
example of an avionics electronic system requiring system development assurance level
A type II and for which the pilot will be within the loop through pilot/system information
exchange
62396-1  IEC:2012(E) – 11 –
3.18
expert
person who has demonstrated competence to apply knowledge and skill to the specific
subject
3.19
firm fault
term used at the aircraft function level. It is a failure that cannot be reset other than by
rebooting the system or by cycling the power to the relevant functional element
Note 1 to entry: Such a fault could impact the value for the MTBF of the LRU and provide no fault found during
subsequent test.
3.20
fly by wire
FBW
example of avionics electronic system requiring system development assurance level A type I
and for which the pilot will not be within the aircraft stability control loop
3.21
functional hazard analysis
FHA
assessment of all hazards against a set of defined hazard classes
3.22
giga electron volt
GeV
radiation particle energy giga electron volts (thousand million electron volts)
Note 1 to entry: The SI equivalent energy is 160,2 picojoules.
3.23
gray
Gy
SI unit of ionising radiation dose and the energy deposited as ionization and excitation (J) per
unit mass (kg)
Note 1 to entry: Related units are centigray (cGy) and rad. 1 cGy is equal to 1 rad.
3.24
hard error
permanent or semi-permanent damage of a cell by atmospheric radiation that is not
recoverable even by cycling the power off and on
3.25
hard fault
term used at the aircraft function level which refers to the permanent failure of a component
within an LRU
Note 1 to entry: A hard fault results in the removal of the LRU affected and the replacement of the permanently
damaged component before a system/system architecture can be restored to full functionality. Such a fault could
impact the value for the MTBF of the LRU repaired.
3.26
heavy ions
positively charged nuclei of the elements heavier than hydrogen and helium

– 12 – 62396-1  IEC:2012(E)
3.27
in-the-loop
test methodology where an LRU is placed within a radiation beam that provides a simulation
of the atmospheric neutron environment and where the inputs to the LRU would be from an
electronic fixture external to the beam to enable a closed loop system
Note 1 to entry: The electronic fixture would contain a host computer for the aircraft simulation model. The
electronic fixture would also contain appropriate signal conditioning for compatibility with the LRU. In the case of
an automatic control function, the outputs from the LRU could be, in turn, sent to an actuation means or directly to
the host computer. The host computer would automatically close a stability loop (as in the case of a fly-by-wire
control system). In the case of a navigation function, the outputs from the LRU could be sent to a display system
where the pilot could then close the navigation loop.
3.28
integrated modular avionics
IMA
implementation of aircraft functions in a multitask computing environment where the
computations for each specific system implementing a particular function are confined to a
partition that is executed by a common computing resource (a single digital electronic circuit)
3.29
latch-up
triggering of a parasitic pnpn circuit in bulk CMOS, resulting in a state where the parasitic
latched current exceeds the holding current. This state is maintained while power is applied
3.30
linear energy transfer
LET
energy deposited per unit path length in a semiconductor along the path of the radiation
Note 1 to entry: The units applicable are MeV⋅cm /mg.
3.31
linear energy transfer threshold
LETth
for a given component, the minimum LET to cause an effect at a particle fluence of
7 2
1 × 10 ions/cm
3.32
line replaceable unit
LRU
piece of avionics electronic equipment that may be replaced during the maintenance cycle of
the system
3.33
mega electron volt
MeV
radiation particle energy mega electron volts (million electron volts)
Note 1 to entry: The SI equivalent energy is 160,2 femtojoule.
3.34
mean time between failure
MTBF
measure of reliability requirements and is the mean time between failure of equipment or a
system in service
62396-1  IEC:2012(E) – 13 –
3.35
mean time between unscheduled removals
MTBUR
measure of reliability requirements and is the mean time between unscheduled removal of
equipment or a system in service
3.36
multiple bit upset
MBU
the energy deposited in the silicon of an electronic component by a single ionising particle
causes upset to more than one bit in the same word
Note 1 to entry: The definition of MBU has been updated due to the introduction of the definition of MCU.
3.37
multiple cell upset
MCU
the energy deposited in the silicon of an electronic component by a single ionising particle
induces several bits in an integrated circuit (IC) to upset at one time
3.38
neutron
elementary particle with atomic mass number of one and which carries no charge
Note 1 to entry: It is a constituent of every atomic nucleus except hydrogen.
3.39
particle fluence
for a unidirectional beam of particles, this is the number of particles crossing unit surface area
at right angles to the beam
Note 1 to entry: For isotropic flux, this is the number entering sphere of unit cross-sectional area.
Note 2 to entry: The units applicable are particles/cm .
3.40
particle flux
fluence rate per unit time
Note 1 to entry: The units applicable are particles/cm ⋅s.
3.41
pion or pi-meson
sub-atomic particle
Note 1 to entry: The charge possibilities are (+1, –1, 0) and they are produced by energetic nuclear interactions.
3.42
preliminary system safety assessment
PSSA
systematic evaluation of a proposed system architecture and implementation based on the
Functional Hazard Assessment and failure condition classification to determine safety
Note 1 to entry: See section 2.2 ARP4761 [118].
3.43
proton
elementary particle with atomic mass number of one and positive electric charge and which is
a constituent of all atomic nuclei

– 14 – 62396-1  IEC:2012(E)
3.44
reliability
R(t)
for a system with constant failure rate, the conditional probability that a system will remain
operational over the time interval 0 to t given by:
–λt
R(t) = e  and λ = 1/MTBF
3.45
risk
measure of the potential inability to achieve overall program objectives within defined cost,
schedule, and technical constraints
3.46
single bit upset
SBU
in a semiconductor device when the radiation absorbed by the device is sufficient to change a
single cell’s logic state
Note 1 to entry: After a new write cycle, the original state can be recovered.
3.47
single event burnout
SEB
burn out of a powered electronic component or part thereof as a result of the energy
absorption triggered by an individual radiation event
3.48
single event effect
SEE
response of a component caused by the impact of a single particle (for example galactic
cosmic rays, solar energetic particles, energetic neutrons and protons)
Note 1 to entry: The range of responses can include both non-destructive (for example upset) and destructive (for
example latch-up or gate rupture) phenomena.
3.49
single event functional interrupt
SEFI
occurrence of an upset, usually in a complex device (e.g. a microprocessor), such that a
control path is corrupted, leading the part to cease to function properly
Note 1 to entry: This effect has sometimes been referred to as lockup, indicating that sometimes the part can be
put into a “frozen” state (see 6.2.6).
3.50
single event gate rupture
SEGR
in the gate of a powered insulated gate component when the radiation charge absorbed by the
device is sufficient to cause gate rupture, which is destructive
3.51
single event latch-up
SEL
in a four layer semiconductor device when the radiation absorbed by the device is sufficient to
cause a node within the powered semiconductor device to be held in a fixed state whatever
input is applied until the device is de-powered, such latch up may be destructive or non-
destructive
62396-1  IEC:2012(E) – 15 –
3.52
single event transient
SET
spurious signal or voltage, induced by the deposition of charge by a single particle that can
propagate through the circuit path during one clock cycle
Note 1 to entry: See 6.2.4 of this document.
3.53
single event upset
SEU
in a semiconductor device when the radiation absorbed by the device is sufficient to change a
cell’s logic state
Note 1 to entry: After a new write cycle, the original state can be recovered.
3.54
single hard error
SHE
single event induced hard error
in a single event the radiation absorbed by the device is sufficient to cause permanent stuck-
bit in the device, and a hard error within the equipment
3.55
soft error
change of state of a latched logic state from one to zero or vice-versa
Note 1 to entry: It is also known as a single event upset.
Note 2 to entry: It is non-destructive and can be rewritten or reset.
3.56
soft fault
term used at the aircraft function level that refers to the characteristic of invalid digital logic
cell(s) state changes within digital hardware electronic circuitry
Note 1 to entry: It is a fault that does not involve replacement of a permanently damaged component within an
LRU but it does involve restoring the logic cells to valid states before a system/system architecture can be restored
to full functionality. Such a fault condition has been suspected in the "no fault found" syndrome for functions
implemented with digital technology and it would probably impact the value for the MTBUR of the involved LRU. If a
soft fault results in the mistaken replacement of a component within the LRU, the replacement could impact the
value for the MTBF of the LRU repaired.
3.57
solar energetic particle (SEP) events
during these periods there is enhancement of solar particles (protons, ions and some
neutrons) caused by solar flare activity or coronal mass ejections
Note 1 to entry: The enhancement can last from a few hours to several days. A small fraction has sufficiently
energetic spectra to produce significantly enhanced secondary neutron fluxes in the atmosphere.
3.58
substitute component
component used as a replacement in equipment after the equipment design has been
approved
Note 1 to entry: In some contexts, the term “alternate component” is used to describe a substitute component that
is “equal to or better than” the original component.
3.59
system safety assessment
SSA
assessment performed to verify compliance with the safety requirements

– 16 – 62396-1  IEC:2012(E)
3.60
system
collection of hardware and software elements that implement a specific aircraft function or set
of aircraft functions
3.61
total ionising dose
TID
cumulative radiation dose that goes into ionization that is received by a device during a
specified period of time
3.62
validation
method of confirmation of component radiation tolerance by the equipment manufacturer,
when there is no in-service data from prior use or radiation data from a test laboratory
4 Abbreviations and acronyms
AC Advisory Circular
AIR atmospheric ionizing radiation
ARP aerospace recommended practices
ASET analogue single event transient
ASIC application specific integrated circuit
BIT built-in test
BPSG borophosphosilicate glass
CECC CENELEC electronic components committee
CMOS complimentary metal oxide semiconductor
COTS commercial-off-the-shelf
D-D deuterium-deuterium
DOE Department Of Energy (USA)
DRAM dynamic random access m
...