adum3211 Analog Devices, Inc., adum3211 Datasheet - Page 18

• Manufacturer Part Number: adum3211
• Description: Dual-channel Digital Isolator, Enhanced System-level Esd Reliability
• Manufacturer: Analog Devices, Inc.

ADuM3210/ADuM3211
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 ADuM321x.
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 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 ADuM321x 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.
A bipolar ac voltage environment is the most stringent. The
goal of a 50-year operating lifetime under the ac bipolar
condition determines the Analog Devices recommended
maximum working voltage.
Rev. C | Page 18 of 20
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 waveform, 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.
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