ADUM1280 AD [Analog Devices], ADUM1280 Datasheet - Page 15

• Manufacturer Part Number: ADUM1280
• Description: 3 kV RMS Dual Channel Digital Isolators
• Manufacturer: AD [Analog Devices]

Data Sheet
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 ADuM128x.
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 19 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
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 ac bipolar condition
determines the Analog Devices recommended maximum
working voltage.
ADuM128x
depends on the
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ADuM1280/ADuM1281/ADuM1285/ADuM1286
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 19 can be applied while main-
taining 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 16
or Figure 17 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 19.
Note that the voltage presented in Figure 17 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
RATED PEAK VOLTAGE
RATED PEAK VOLTAGE
0V
0V
0V
Figure 16. Unipolar AC Waveform
Figure 15. Bipolar AC Waveform
Figure 17. DC Waveform