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 9-1 for TDDB test setup. The insulation breakdown data is collected at various high voltages switching at 60Hz over temperature. For reinforced insulation, VDE standard requires the use of TDDB projection line with failure rate of less than 1 part per million (ppm) and a minimum insulation lifetime of 20 years. VDE standard also requires additional safety margin of 20% for working voltage and 50% for insulation lifetime which translates into minimum required life time of 30 years.  

Figure 9-2 shows the intrinsic capability of the isolation barrier to withstand high voltage stress over its lifetime. Based on the TDDB data, the intrinsic capability of these devices is 400V_RMS 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. The working voltage of the D-8 package is specified up to 400V_RMS. At the lower working voltages, the corresponding insulation barrier life time is much longer.

Figure 9-1 Test Setup for Insulation Lifetime Measurement

Figure 9-2 Insulation Lifetime Projection Data