www.ti.com

Table of Contents

Technical White Paper

Why are Digital Isolators Certified to Meet ElectricalEquipment Standards?

ABSTRACT
If you look at typical data sheets of digital isolators from Texas Instruments, you will notice that thesesemiconductor components are certified to a number of international electrical equipment standards such as
IEC 62368-1, IEC 60601-1 and IEC 61010-1. These standards outline safety requirements for audio/video,communication, information technology, medical, measurement, control, and laboratory use equipment;
Figure 1-1 shows some common electrical equipment that use digital isolators for insulation. Now, you may
be wondering how and why a digital isolator, which is one small component of a large and complex piece ofequipment, is certified to the equipment standards? We’ll explore this subject here.

Figure 1-1. Common Electrical Equipment that use Certified Digital Isolators

Table of Contents
1 Introduction.............................................................................................................................................................................22 Critical Distances....................................................................................................................................................................2
3 Environmental Tests...............................................................................................................................................................24 High-Voltage Tests..................................................................................................................................................................25 Conclusion.............................................................................................................................................................................. 36 References.............................................................................................................................................................................. 3

List of Figures
Figure 1-1. Common Electrical Equipment that use Certified Digital Isolators............................................................................ 1

List of Tables
Table 4-1. IEC Standard Clauses Used to Certify Digital Isolators.............................................................................................. 3

Trademarks
All trademarks are the property of their respective owners.

SLLA564 – NOVEMBER 2021
Submit Document Feedback

Why are Digital Isolators Certified to Meet Electrical Equipment Standards?
Copyright © 2021 Texas Instruments Incorporated

1

Introduction

www.ti.com

1 Introduction
Although the equipment has to comply with all required clauses of the standard, semiconductor components
such as digital isolators are only certified to specific clauses of the standard that deal with high voltage insulationand safety. When equipment manufacturers pick certified digital isolators for their design, they are confident thatthe insulation performance has already been verified by a third-party certification agency. Also, the equipment
manufacturer will not need to repeat the time consuming and expensive insulation-related environmental andhigh voltage tests when they certify their equipment. To certify digital isolators, approving agencies needtechnology and inner construction details of the semiconductor components. This information can easily beshared by the manufacturers of these devices with the agencies. This makes the equipment certifications
process a lot easier by cutting down on time and expense. Therefore, it should not come as a surprise that
equipment manufacturers prefer to design with certified digital isolators.
Now we will discuss the various standard clauses that deal with digital isolators. We can broadly place theseclauses in three categories: critical distances, environmental tests and high voltage tests.

2 Critical Distances
Creepage, clearance, and distance through insulation (DTI) are critical distances that are evaluated in any
equipment certification of digital isolators. Clearance is the shortest distance in air between two conductive
parts and creepage is the shortest distance along the surface of a solid insulation material between two
conductive parts across the isolation barrier. DTI, on the other hand, is the shortest distance within an insulating
material interposed between two conductive parts. For digital isolators, the primary insulation is provided bythin-film layers of silicon dioxide (SiO2) or polymer-based dielectric applied across a high voltage capacitor ortransformer. Additionally, the mold compound coating between the two sides of the isolator provide secondary
insulation. The digital isolators are designed so that the high voltage breakdown almost always occurs acrossthe thin-film dielectric layers of the capacitor or transformer. Insulation voltage ratings depend on the quality ofsolid insulation used and length of these critical distances.

3 Environmental Tests
Digital isolators are subjected to environmental stresses such as thermal cycling, humidity and maximum
operating temperature tests to ensure long-term reliability of the insulation under adverse conditions. During
thermal cycling tests, a component is subjected to cold and hot temperature cycles for at least 3 days. The
sample is subjected 10 times to such cycles of temperature variation. So, the minimum stress time for thermal
cycling is 30 days. Humidity conditioning is typically carried out for two days in a chamber containing air witha relative humidity of 93% ± 3% and temperature is maintained within 2 °C of any value between 20 °C and42 °C so that condensation does not occur. For tropical conditions, the time duration is increased to five days.
Maximum temperature test is performed when the device is operated in worst-case ambient temperature andother conditions such as supply voltage, frequency, and external loadings. The digital isolator is operated in thismode until thermal stability is achieved.

4 High-Voltage Tests
Each of the three equipment standards mentioned earlier require digital isolators to be subjected to dielectric
tests after thermal cycling, humidity and maximum temperature tests. The dielectric test after thermal cycling
and humidity preconditioning is performed according to the voltage specification of each standard for basic andreinforced insulation, but the test voltage is multiplied by 1.6. This 60% margin is added on top of the alreadyhigh transient voltage due to thinner DTI of digital isolators. The 60% dielectric test margin is not required
after maximum operating temperature test. IEC 60601-1, Medical equipment standard, requires an additional
defibrillation-proof test which requires 5000 VDC discharges of both positive and negative polarities applied tothe digital isolator. This is followed by a 4000 VRMS dielectric test across the isolation barrier. Finally, the moldcompound coatings used by the digital isolators need to be evaluated for Comparative Tracking Index (CTI)
according to IEC 60112 to determine their resistance against tracking or carbonization under consistently highworking voltage stress. Mold compounds with the best performance are classified as Material Group I and they
have CTI ≥ 600 V and the lowest category or Material Group IIIB mold compounds have CTI between 100 V andjust under 175 V.

2Why are Digital Isolators Certified to Meet Electrical Equipment Standards?
Copyright © 2021 Texas Instruments Incorporated

SLLA564 – NOVEMBER 2021
Submit Document Feedback

www.ti.com

Conclusion

Table 4-1 summarizes the clauses of the three most common IEC standards that are used to certify digitalisolators for use in high voltage safety applications.
Table 4-1. IEC Standard Clauses Used to Certify Digital Isolators
Evaluation

Clause of Standard
IEC 62368-1: 2018

IEC 60601-1 Ed3:2005 +A1:2012 IEC 61010-1: Ed3:2010+A1:2016

Creepage

5.4.3

8.9

6.7.2.1 orTables K.1 to K.4

Clearance

5.4.2

8.9

6.7.2.1 orTables K.1 to K.4

Distance through insulation

5.4.4.2 or evaluated by 5.4.4.4,
5.4.7

8.8.2 and/or evaluated by 8.9.3.2 6.7.2.2.2 or Table K.9 or Layers.
and/or Layers and/or 8.9.3.3
N/A for reinforced; Accepted per
clause 14.1a) based on IEC
62368-1.

Thermal cycling

5.4.1.5.3, 5.4.7

8.9.3.4

6.7.2.2.2
Form A.17

Humidity

5.4.8, Five days (tropical)

5.7, Two days

6.8.2, Two days

Dielectric after thermal cycling

5.4.9.1, times 1.6 (for 60%margin)8.8.3, times 1.6 (for 60% margin)

6.7.2.2.1 or Tables K.1 to K.7
times 1.6 (for 60% margin)Temperature test

5.4.1.4

1110

Dielectric after temperaturetest

5.4.9.1

8.8.3

6.7.2 or Tables K.1 to K.7

Defibrillation test

N/A

8.5.5.1

N/A

IEC 60112 evaluation andmaterial classification

5.4.3.3

8.9.1.7

6.7.1.3

5 Conclusion
Certification of digital isolators to equipment standards is not only possible but highly recommended forsemiconductor suppliers as it makes the equipment manufacturer’s safety approval process much easier.
Additionally, semiconductor suppliers are in the best position to provide digital isolators’ construction details
to certification agencies as required. Digital isolators are certified to specific clauses of these standards that deal
with high voltage insulation and safety. Equipment manufacturers will almost always choose a certified digitalisolator for use in their equipment than one that is not certified.
For a complete list of certified isolators from Texas Instruments, see Digital Isolators – Certifications.

6 References
1. IEC 62368-1 Edition 3.0, Audio/video, information and communication technology equipment – Part 1: Safety
requirements, October 2018
2. IEC 60601-1 Edition 3.0+A1, Medical electrical equipment – Part 1: General requirements for basic safety
and essential performance, December 2005 and July 2012
3. IEC 61010-1 Edition 3.0+A1, Safety requirements for electrical equipment for measurement, control, andlaboratory use – Part 1: General requirements, June 2010 and December 2016
4. IEC 60112 Edition 5.0, Method for the determination of the proof and the comparative tracking indices ofsolid insulating materials, October 2020

SLLA564 – NOVEMBER 2021
Submit Document Feedback

Why are Digital Isolators Certified to Meet Electrical Equipment Standards?
Copyright © 2021 Texas Instruments Incorporated3IMPORTANT NOTICE AND DISCLAIMERTI PROVIDES TECHNICAL AND RELIABILITY DATA (INCLUDING DATA SHEETS), DESIGN RESOURCES (INCLUDING REFERENCEDESIGNS), APPLICATION OR OTHER DESIGN ADVICE, WEB TOOLS, SAFETY INFORMATION, AND OTHER RESOURCES “AS IS”
AND WITH ALL FAULTS, AND DISCLAIMS ALL WARRANTIES, EXPRESS AND IMPLIED, INCLUDING WITHOUT LIMITATION ANYIMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT OF THIRDPARTY INTELLECTUAL PROPERTY RIGHTS.
These resources are intended for skilled developers designing with TI products. You are solely responsible for (1) selecting the appropriate
TI products for your application, (2) designing, validating and testing your application, and (3) ensuring your application meets applicablestandards, and any other safety, security, regulatory or other requirements.
These resources are subject to change without notice. TI grants you permission to use these resources only for development of anapplication that uses the TI products described in the resource. Other reproduction and display of these resources is prohibited. No license
is granted to any other TI intellectual property right or to any third party intellectual property right. TI disclaims responsibility for, and you
will fully indemnify TI and its representatives against, any claims, damages, costs, losses, and liabilities arising out of your use of theseresources.
TI’s products are provided subject to TI’s Terms of Sale or other applicable terms available either on ti.com or provided in conjunction withsuch TI products. TI’s provision of these resources does not expand or otherwise alter TI’s applicable warranties or warranty disclaimers for
TI products.
TI objects to and rejects any additional or different terms you may have proposed. IMPORTANT NOTICE
Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265
Copyright © 2022, Texas Instruments Incorporated