ADuM7440/ADuM7441/ADuM7442 Data Sheet
Rev. D | Page 16 of 20
The insulation lifetime of the ADuM7440/ADuM7441/
ADuM7442 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 20, Figure 21, and Figure 22
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 18 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 21 or
Figure 22 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 18.
Note that the voltage presented in Figure 21 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
08340-011
Figure 20. Bipolar AC Waveform
0V
RATED PEAK VOLTAGE
08340-012
Figure 21. Unipolar AC Waveform
0V
RATED PEAK VOLTAGE
08340-013
Figure 22. DC Waveform
