**3. High voltage performances**

Isolation rating is defined by the maximum withstand voltage with 1 min duration per UL1577. For production test, the digital isolators were tested for 1 s at 120% of rated voltage. For example, for 2.5 kVrms, 1 min-rated digital isolators, the production test is 3 kVrms for 1 s. For practical applications, there are two important high voltage performance parameters; one is the maximum working voltage where the insulation needs to be intact over the lifetime of continuous operation, AC or DC. For example, per VDE0884-11, the lifetime for isolators with reinforced isolation at 120% of the rated voltage needs to be greater than 37.5 years at 1 ppm failure rate. As an example, if the rated working voltage for a reinforced digital isolator is 1 kVrms, its lifetime at 1.2 kVrms needs to be greater than 37.5 years at 1 ppm failure rate. Similarly, the lifetime for isolators with basic insulation at 120% of the rated voltage needs to be better than 26 years with 1000 ppm failure. The other important application specification is the maximum transient isolation voltage where the part needs to survive. Transient test waveforms may vary, and an example waveform per EN 60747-5-5 or IEC 61010-1 is shown in **Figure 5**. It rise time from 10–90% is about 1.2 μS, while the falling time from peak to 50% is 50 μS. This intends to simulate the lightening condition, so it is important for isolators to have robust surge performance to be robust in the field. ESD tolerance is an important attribute for semiconductor devices, and high surge performance also implies excellent ESD performance.

**Figure 5.** *IEC61010-1 Surge test waveform.*
