Data Sheet
For example, at a magnetic field frequency of 1 MHz, the
maximum allowable magnetic field of 0.2 kgauss induces a
voltage of 0.25 V at the receiving coil. This is about 50% of the
sensing threshold and does not cause a faulty output transition.
Similarly, if such an event occurs during a transmitted pulse
(and has the worst-case polarity), it reduces the received pulse
from >1.0 V to 0.75 V—still well above the 0.5 V sensing
threshold of the decoder.
The preceding magnetic flux density values correspond to
specific current magnitudes at given distances away from the
ADuM120x transformers. Figure 14 expresses these allowable
current magnitudes as a function of frequency for selected
distances. As seen, the ADuM120x are extremely immune and
can be affected only by extremely large currents operating very
close to the component at a high frequency. For the 1 MHz
example, a 0.5 kA current would have to be placed 5 mm away
from the ADuM120x to affect the operation of the component.
1000
MAXIMUM ALLOWABLE CURRENT (kA)
ADuM1200/ADuM1201
POWER CONSUMPTION
The supply current at a given channel of the ADuM120x
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)
I
DDI
=
I
DDI (D)
× (2f −
f
r
) +
I
DDI (Q)
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.
f
≤ 0.5f
r
f
> 0.5f
r
DISTANCE = 1m
100
10
DISTANCE = 100mm
1
DISTANCE = 5mm
0.1
1k
10k
100k
1M
10M
100M
MAGNETIC FIELD FREQUENCY (Hz)
Figure 14. Maximum Allowable Current for Various
Current-to-ADuM120x 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. Care should be taken in the layout of such traces to
avoid this possibility.
Rev. I | Page 25 of 28
04642-014
0.01
AD [ ANALOG DEVICES ]
