Data Sheet ADuM3210/ADuM3211
Rev. K | Page 19 of 21
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 ADuM3210/ADuM3211.
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 31 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 the 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 ADuM3210/ADuM3211 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 15, Figure 16, and Figure 17 illustrate these different
isolation voltage waveforms.
Bipolar ac voltage is the most stringent environment. The goal
of a 50-year operating lifetime under the bipolar ac condition
determines the maximum working voltage recommended by
Analog Devices.
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 31 can be applied while maintaining the
50-year minimum lifetime, provided that the voltage conforms
to either the unipolar ac or dc voltage cases.
Any cross-insulation voltage waveform that does not conform
to Figure 16 or Figure 17 should be treated as a bipolar ac wave-
form, and its peak voltage should be limited to the 50-year lifetime
voltage value listed in Table 31.
Note that the voltage presented in Figure 16 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
06866-012
Figure 15. Bipolar AC Waveform
0V
RATED PEAK VOLTAGE
06866-013
Figure 16. Unipolar AC Waveform
0V
RATED PEAK VOLTAGE
06866-014
Figure 17. DC Waveform
