ADuM1440/ADuM1441/ADuM1442/ADuM1445/ADuM1446/ADuM1447 Data Sheet
Rev. E | Page 22 of 25
1k
100M10k
MAXIMUM ALLOWABLE CURRENT (kA)
100k 1M
10M
MAGNETIC FIELD FREQUENC
Y (Hz)
DISTANCE = 5mm
DISTANCE = 100mm
DISTANCE = 1m
1000
100
10
1
0.1
0.01
11845-021
Figure 33. Maximum Allowable Current for Various Current-to-ADuM1440/
ADuM1441/ADuM1442/ADuM1445/ADuM1446/ADuM1447 Spacings
Note that at combinations of strong magnetic field and high
frequency, any loops formed by PCB traces can induce error
voltages sufficiently large enough to trigger the thresholds of
succeeding circuitry. Take care in the layout of such traces to
avoid this possibility.
POWER CONSUMPTION
The supply current at a given channel of the ADuM1440/
ADuM1441/ADuM1442/ADuM1445/ADuM1446/ADuM1447
isolator is a function of the supply voltage, the data rate of the
channel, and the output load of the channel.
For each input channel, the supply current is given by
I
DDI
= I
DDI (Q)
f ≤ 0.5 f
r
I
DDI
= I
DDI (D)
× (2f − f
r
) + I
DDI (Q)
f > 0.5 f
r
For each output channel, the supply current is given by
I
DDO
= I
DDO (Q)
f ≤ 0.5 f
r
I
DDO
= (I
DDO (D)
+ (0.5 × 10
−3
) × C
L
× V
DDO
) × (2f − f
r
) + I
DDO (Q)
f > 0.5 f
r
where:
I
DDI (D)
, I
DDO (D)
are the input and output dynamic supply currents
per channel (mA/Mbps).
I
DDI (Q)
, I
DDO (Q)
are the specified input and output quiescent
supply currents (mA).
f is the input logic signal frequency (MHz); it is half the input
data rate, expressed in units of Mbps.
f
r
is the input stage refresh rate (Mbps).
C
L
is the output load capacitance (pF).
V
DDO
is the output supply voltage (V).
To calculate the total V
DD1
and V
DD2
supply current, the supply
currents for each input and output channel corresponding to
V
DD1
and V
DD2
are calculated and totaled. Figure 11 through
Figure 18 show per channel supply currents as a function of
data rate for an unloaded output condition.
The ADuM1440/ADuM1441/ADuM1442/ADuM1445/
ADuM1446/ADuM1447 devices are intended to operate at an
ultralow current. This is achieved by operating the part at a low
average data rate, either by bursting data at high speed at a low
duty factor or by running low bit rates. If data is burst at high
data rates, the part sits quiescent for the majority of the time, at
low data rates, the power consumption approaches the
quiescent power consumption. Table 25 shows the typical
current for an input and output channel pair as well as the total
power dissipated for that channel. The total power is summed
across both sides of the device, so the power is being drawn
from two different supplies. However, it shows how the power
depends on the V
DD
values and the state of the refresh.
Table 25. Typical Total Power Dissipation Per Channel
State of
Refresh
Typical Input
Channel
Typical Output
Channel
Power/Ch
V
DDI
I
DDI(Q)
V
DDO
I
DDO(Q)
Enabled
2.5 V 2.6 µA 2.5 V 0.5 µA 7.8 µW
3.3 V 4.8 µA 3.3 V 0.8 µA 18.5 µW
Disabled
2.5 V 0.05 µA 2.5 V 0.05 µA 0.3 µW
3.3 V 0.12 µA 3.3 V 0.13 µA 0.8 µW
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 ADuM1440/
ADuM1441/ADuM1442/ADuM1445/ADuM1446/ADuM1447.
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 20 summarize the
peak voltage for 50 years of service life for a bipolar ac operating
condition and the maximum CSA 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 ADuM1440/ADuM1441/
ADuM1442/ADuM1445/ADuM1446/ADuM1447 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 34, Figure 35, and Figure 36 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.
