Data Sheet
ADuM1400/ADuM1401/ADuM1402
In the case of unipolar ac or dc voltage, the stress on the
insulation is significantly lower, which allows operation at
higher working voltages while still achieving a 50-year service
life. The working voltages listed in Table 14 can be applied while
maintaining the 50-year minimum lifetime, provided the voltage
conforms to either the unipolar ac or dc voltage cases. Any cross-
insulation voltage waveform that does not conform to Figure 22
or Figure 23 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 14.
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 ADuM140x.
Analog Devices performs accelerated life testing using voltage
levels higher than the rated continuous working voltage. Accel-
eration 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 14 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 a 50-year service life voltage. Operation at these high working
voltages can lead to shortened insulation life in some cases.
Note that the voltage presented in Figure 22 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.
RATED PEAK VOLTAGE
0V
Figure 21. Bipolar AC Waveform
The insulation lifetime of the ADuM140x 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 21, Figure 22, and Figure 23 illustrate these
different isolation voltage waveforms, respectively.
RATED PEAK VOLTAGE
0V
Figure 22. Unipolar AC Waveform
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.
RATED PEAK VOLTAGE
0V
Figure 23. DC Waveform
Rev. H | Page 29 of 32
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