ADuM1200/ADuM1201
INSULATION LIFETIME
All insulation structures eventually break down when subjected
to voltage stress over a sufficiently long period. The rate of insu-
lation 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 ADuM120x.
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 volt-
ages. 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 ADuM120x 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, respectively.
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.
Data Sheet
In the case of unipolar ac or dc voltage, the stress on the insu-
lation is significantly lower, which allows operation at higher
working voltages yet still achieves a 50-year service life. The
working voltages listed in Table 14 can be applied while main-
taining 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 16
or Figure 17 is to be treated as a bipolar ac waveform, and its
peak voltage is to be limited to the 50-year lifetime voltage value
listed in Table 14.
Note that the voltage presented in Figure 16 is shown as sinu-
soidal 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
04642-021
Figure 15. Bipolar AC Waveform
RATED PEAK VOLTAGE
04642-022
0V
Figure 16. Unipolar AC Waveform
RATED PEAK VOLTAGE
04642-023
0V
Figure 17. DC Waveform
Rev. I | Page 26 of 28
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