Data Sheet ADuM7234
Rev. B | Page 9 of 12
GND
1
V
DD1
ΔV
Δt
ΔV
Δt
5V
GND
1
V
DD1
15V
15V
GND
A
AND GND
B
V
DDA
AND V
DDB
5V
GND
A
AND GND
B
V
DDA
AND V
DDB
15V
15V
07990-006
Figure 11. Common-Mode Transient Immunity Waveforms, Input to Output
GND
A
/GND
B
V
DDB
/V
DDA
ΔV
Δt
ΔV
Δt
15V
GND
A
/GND
B
V
DDA
/V
DDB
15V
15V
GND
A
/GND
B
V
DDA
/V
DDB
15V
GND
B
/GND
A
V
DDB
/V
DDA
15V
15V
07990-007
Figure 12. Common-Mode Transient Immunity Waveforms
Between Outputs
GND
A
/GND
B
V
DDA
/V
DDB
V
DDA
/V
DDB
GND
A
/GND
B
ΔV
DD
Δt
07990-008
Figure 13. Transient Immunity Waveforms, Output Supplies
INSULATION LIFETIME
All insulation structures eventually break down when subjected
to voltage stress over a sufficiently long period. The rate of insu-
lation degradation depends on the characteristics of the voltage
waveform applied across the insulation. In addition to the testing
performed by the regulatory agencies, Analog Devices conducts
an extensive set of evaluations to determine the lifetime of the
insulation structure within the ADuM7234.
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. Table 3 lists the peak voltage for 50 years of
service life for a bipolar ac operating condition and the maximum
Analog Devices recommended working voltage. 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 ADuM7234 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 14, Figure 15, and Figure 16 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
voltage listed in Table 3 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 15 or Figure 16
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 3.
Note that the voltage presented in Figure 15 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.
0V
RATED PEAK VOLTAGE
07990-009
Figure 14. Bipolar AC Waveform
0V
RATED PEAK VOLTAGE
07990-010
Figure 15. Unipolar AC Waveform
0V
RATED PEAK VOLTAGE
07990-011
Figure 16. DC Waveform
