Datasheet

Data Sheet ADuM1200/ADuM1201
Rev. K | Page 25 of 28
MAGNETIC FIELD FREQUENCY (Hz)
MAXIMUM ALLOWABLE CURRENT (kA)
1000
100
10
1
0.1
0.01
1k
10k 100M
100k 1M 10M
DISTANCE = 5mm
DISTANCE = 1m
DISTANCE = 100mm
04642-014
Figure 14. Maximum Allowable Current for Various
Current-to-ADuM1200/ADuM1201 Spacings
Note that, at combinations of strong magnetic fields and high
frequencies, any loops formed by PCB traces can induce suffi-
ciently large error voltages to trigger the threshold 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 ADuM1200/
ADuM1201 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 ≤ 0.5f
r
I
DDI
= I
DDI (D)
× (2f − f
r
) + I
DDI (Q)
f > 0.5f
r
For each output channel, the supply current is given by
I
DDO
= I
DDO (Q)
f ≤ 0.5f
r
I
DDO
= (I
DDO (D)
+ (0.5 × 10
−3
) × C
L
V
DDO
) × (2f − f
r
) + I
DDO (Q)
f > 0.5f
r
where:
I
DDI (D)
, I
DDO (D)
are the input and output dynamic supply currents
per channel (mA/Mbps).
C
L
is the output load capacitance (pF).
V
DDO
is the output supply voltage (V).
f is the input logic signal frequency (MHz, half of the input data
rate, NRZ signaling).
f
r
is the input stage refresh rate (Mbps).
I
DDI (Q)
, I
DDO (Q)
are the specified input and output quiescent
supply currents (mA).
To calculate the total I
DD1
and I
DD2
supply currents, the supply
currents for each input and output channel corresponding to
I
DD1
and I
DD2
are calculated and totaled. Figure 6 and Figure 7
provide per-channel supply currents as a function of data rate
for an unloaded output condition. Figure 8 provides per-
channel supply current as a function of data rate for a 15 pF
output condition. Figure 9 through Figure 11 provide total
V
DD1
and V
DD2
supply current as a function of data rate for
ADuM1200 and ADuM1201 channel configurations.
INSULATION LIFETIME
All insulation structures eventually break down when subjected
to voltage stress over a sufficiently long period. The rate of insu-
lation 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 ADuM1200/ADuM1201.
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. The values shown in Table 14 summarize the
peak voltage for 50 years of service life for a bipolar ac operating
condition and the maximum CSA/VDE approved working volt-
ages. 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 ADuM1200/ADuM1201 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, respectively.
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.
In the case of unipolar ac or dc voltage, the stress on the insu-
lation is significantly lower, which allows operation at higher
working voltages yet still achieves a 50-year service life. The
working voltages listed in Table 14 can be applied while main-
taining the 50-year minimum lifetime provided 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 is to be treated as a bipolar ac waveform, and the
peak voltage is to be limited to the 50-year lifetime voltage value
listed in Table 14.
Note that the voltage presented in Figure 16 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
04642-021
Figure 15. Bipolar AC Waveform