A customer is asking us what the minimum DTI is and whether or not we can support reinforced insulation. Can you comment?
The minimum distance through insulation (DTI) for iCoupler products is 17 µm (0.017 mm). Many system level standards have a 0.4 mm DTI requirement for material used as solid insulation. However, system level standards such as IEC 60950 also recognize that specific varieties of insulation such as IC potting material, PCB material, and insulating films have different properties than other types of solid insulation. Therefore different rules apply for each material type. Mold compound can be thinner than 0.4 mm if there are type tests and routine tests that proof the insulation. Thin films can be reinforced insulation if there are multiple layers and again type and routine testing is performed. All iCoupler products are tested at production to meet these requirements.
The component level standards IEC 60747, VDE 0884-10 and UL 1577 determine insulation quality through type testing and routine testing rather than structural requirements. In most cases the component standard can be used instead of meeting structural requirements of system level standards. So again the DTI requirements do not apply.
Another requirement for reinforced insulation is a 6kVpk surge rating. This is demonstrated by proof testing at 10 kVpk by the certification agency. All of ADI’s reinforced isolators have passed this testing. Capacitive digital isolators often have difficulty meeting the 10 kVpk surge requirement due to the thick SiO2 films required. Thicker oxide layers can pose manufacturing challenges and reduce the coupling efficiency across the barrier. These challenges can be overcome at the expense of performance and power consumption.
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