Insulation lifetime projection data is collected by using industry-standard Time Dependent Dielectric Breakdown (TDDB) test method. In this test, all pins on each side of the barrier are tied together creating a two-terminal device and high voltage applied between the two sides; See Figure 8-7 for TDDB test setup. The insulation breakdown data is collected at various high voltages switching at 60Hz over temperature. For basic insulation, VDE standard requires the use of TDDB projection line with failure rate of less than 1000 part per million (ppm). For reinforced insulation, VDE standard requires the use of TDDB projection line with failure rate of less than 1 part per million (ppm).

Even though the expected minimum insulation lifetime is 20 years, at the specified working isolation voltage, VDE basic and reinforced certifications require additional safety margin of 20% for working voltage. For basic certification, device lifetime requires a safety margin of 20% translating to a minimum required insulation lifetime of 24 years at a working voltage that is 20% higher than the specified value. For reinforced insulation, device lifetime requires a safety margin of 50% translating to a minimum required insulation lifetime of 30 years at a working voltage that is 20% higher than the specified value

Figure 8-8 and Figure 8-9 show the intrinsic capability of the isolation barrier to withstand high voltage stress over the lifetime of the barrier. Based on the TDDB data, the intrinsic capability of the insulation is 1060V_RMS in the 8-DWV package and 450V_RMS in the 8D package with a lifetime of >100 years. Other factors, such as package size, pollution degree, material group, and so forth. can further limit the working voltage of the component.