Datasheet

ADuM1310/ADuM1311 Data Sheet
Rev. K | Page 20 of 24
INSULATION LIFETIME
All insulation structures eventually break down when subjected
to voltage stress over a sufficiently long period. The rate of
insulation degradation is dependent on the characteristics of the
voltage waveform applied across the insulation. In addition to
the testing performed by the regulatory agencies, Analog
Devices carries out an extensive set of evaluations to determine
the lifetime of the insulation structure within the ADuM1310/
ADuM1311.
Analog Devices performs accelerated life testing using voltage
levels higher than the rated continuous working voltage.
Acceleration factors for several operating conditions are
determined. These factors allow calculation of the time to
failure at the actual working voltage. The values shown in Table 10
summarize the peak voltage for 50 years of service life for a
bipolar ac operating condition and the maximum CSA/VDE
approved working voltages. In many cases, the approved
working voltage is higher than 50-year service life voltage.
Operation at these high working voltages can lead to shortened
insulation life in some cases.
The insulation lifetime of the ADuM1310/ADuM1311 depends
on the voltage waveform type imposed across the isolation
barrier. The iCoupler insulation structure degrades at different
rates depending on whether the waveform is bipolar ac,
unipolar ac, or dc. Figure 17, Figure 18, and Figure 19 illustrate
these different isolation voltage waveforms.
Bipolar ac voltage is the most stringent environment. The goal
of a 50-year operating lifetime under the ac bipolar condition
determines the Analog Devices recommended maximum
working voltage.
In the case of unipolar ac or dc voltage, the stress on the
insulation is significantly lower. This allows operation at higher
working voltages while still achieving a 50-year service life. The
working voltages listed in Table 10 can be applied while
maintaining the 50-year minimum lifetime provided the voltage
conforms to either the unipolar ac or dc voltage case. Any cross-
insulation voltage waveform that does not conform to Figure 18
or Figure 19 should be treated as a bipolar ac waveform, and its
peak voltage should be limited to the 50-year lifetime voltage
value listed in Table 10.
Note that the voltage presented in Figure 18 is shown as
sinusoidal for illustration purposes only. It is meant to represent
any voltage waveform varying between 0 V and some limiting
value. The limiting value can be positive or negative, but the
voltage cannot cross 0 V.
0V
RATED PEAK VOLTAGE
04904-017
Figure 17. Bipolar AC Waveform
0V
RATED PEAK VOLTAGE
04904-018
Figure 18. Unipolar AC Waveform
0V
RATED PEAK VOLTAGE
04904-019
Figure 19. DC Waveform
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