Data Sheet
ADuM1240/ADuM1241/ADuM1245/ADuM1246
approved working voltages. In many cases, the approved working
voltage is higher than 50-year service life voltage. Operation at
these high working voltages can lead to shortened insulation
life, in some cases.
POWER CONSUMPTION
The supply current with refresh enabled at a given channel of
the ADuM1240/ADuM1241/ADuM1245/ADuM1246 isolators,
is a function of the supply voltage, the data rate of the channel,
and the output load of the channel.
The insulation lifetime of the ADuM1240/ADuM1241/
ADuM1245/ADuM1246 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 19, Figure 20,
and Figure 21 illustrate these different isolation voltage waveforms.
For each input channel, the supply current is given by
I
DDI = IDDI (Q)
f ≤ 0.5 fr
f > 0.5 fr
IDDI = IDDI (D) × (2f − fr) + IDDI (Q)
For each output channel, the supply current is given by
DDO = IDDO (Q) f ≤ 0.5 fr
DDO = (IDDO (D) + (0.5 × 10−3) × CL × VDDO) × (2f − fr) + IDDO (Q)
f > 0.5 fr
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.
I
I
where:
DDI (D) and IDDO (D) are the input and output dynamic supply
currents per channel (mA/Mbps).
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 maintain-
ing the 50-year minimum lifetime, provided the voltages conform
to either the unipolar ac or dc voltage case. Treat any cross-
insulation voltage waveform that does not conform to Figure 33
or Figure 34 as a bipolar ac waveform, and limit its peak voltage
to the 50-year lifetime voltage value listed in Table 18.
I
CL is the output load capacitance (pF).
VDDO is the output supply voltage (V).
f is the input logic signal frequency (MHz); it is half the input
data rate, expressed in units of Mbps.
fr is the input stage refresh rate (Mbps) = 1/Tr (µs).
I
DDI (Q) and IDDO (Q) are the specified input and output quiescent
supply currents (mA).
Note that the voltage presented in Figure 33 is shown as
sinusoidal for illustration purposes only. It represents any
voltage waveform varying between 0 V and some limiting value.
The limiting value can be positive or negative, but the voltage
must not cross 0 V.
To calculate the total VDD1 and VDD2 supply current, the supply
currents for each input and output channel corresponding to
V
DD1 and VDD2 are calculated and totaled. Figure 9 through
Figure 16 show per channel supply currents as a function of
data rate for an unloaded output condition.
RATED PEAK VOLTAGE
INSULATION LIFETIME
0V
All insulation structures eventually degrade, when subjected to
voltage stress for 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
Figure 32. Bipolar AC Waveform
RATED PEAK VOLTAGE
0V
ADuM1240/ADuM1241/ADuM1245/ADuM1246.
Figure 33. Unipolar AC Waveform
Analog Devices performs accelerated life testing using voltage
levels higher than the rated continuous working voltage.
RATED PEAK 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 18
summarize the peak voltage for 50 years of service life for a
bipolar ac operating condition, and the maximum CSA/VDE
0V
Figure 34. DC Waveform
Rev. A | Page 19 of 24
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