3 Why International Standards for High Voltage Components Have Minimum DTI Requirements

Many International Electro-technical Commission (IEC) system-level safety standards have minimum DTI requirements for components that provide high voltage insulation. This is because dielectric thickness and quality determine the electric field withstand capability of isolators. Historically, optocouplers have been used as isolators in high voltage applications and therefore many safety standards ended up with much thicker DTI requirement, such as a minimum of 0.4 mm, 0.6 mm, or 1 mm for increasing working voltage ratings. These DTI thickness requirements correspond to the voltage withstand capability of the lower quality insulation material used by optocouplers and other legacy isolators. Since digital isolators use newer isolation technologies and high-quality dielectric material, such as silicon dioxide (SiO₂), they do not need to be thick to provide high-quality insulation.