Data Sheet ADuM1310/ADuM1311
Rev. K | Page 19 of 24
04904-015
MAGNETIC FIELD FREQUENCY (Hz)
MAXIMUM ALLOWABLE MAGNETIC FLUX
DENSITY (kgauss)
1k
0.001
100
100M
10
1
0.1
0.01
10k 100k 1M 10M
Figure 15. Maximum Allowable External Magnetic Flux Density
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 occurred during a transmitted pulse
(and had the worst-case polarity), it would reduce 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 from the
ADuM1310/ADuM1311 transformers. Figure 16 expresses
these allowable current magnitudes as a function of frequency
for selected distances. As shown, the ADuM1310/ADuM1311 is
extremely immune and can be affected only by extremely large
currents operated at high frequency very close to the component.
For the 1 MHz example noted, a 0.5 kA current would have to
be placed 5 mm away from the ADuM1310/ ADuM1311 to
affect the component’s operation.
MAGNETIC FIELD FREQUENCY (Hz)
MAXIMUM ALLOWABLE CURRENT (kA)
1000
100
10
1
0.1
0.01
1k
10k 100M100k 1M 10M
DISTANCE = 5mm
DISTANCE = 1m
DISTANCE = 100mm
04904-016
Figure 16. Maximum Allowable Current
for Various Current-to-ADuM1310/ADuM1311 Spacings
Note that, at combinations of strong magnetic field and high
frequency, any loops formed by printed circuit board traces can
induce error voltages sufficient to trigger succeeding circuitry.
Care should be taken in the layout of such traces to avoid this
possibility.
POWER CONSUMPTION
The supply current at a given channel of the ADuM1310/
ADuM1311 isolator is a function of the supply voltage, the
channel data rate, and the channel output load.
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).
C
L
is the output load capacitance (pF).
V
DDO
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.
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 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. The ADuM1310/
ADuM1311 contains an internal data channel that is not
available to the user. This channel is in the same orientation as
Channel A and consumes quiescent current. The contribution
of this channel must be included in the total quiescent current
calculation for each supply. Figure 6 and Figure 7 show per-
channel supply currents as a function of data rate for an
unloaded output condition. Figure 8 shows per-channel supply
current as a function of data rate for a 15 pF output condition.
Figure 9 through Figure 12 show total V
DD1
and V
DD2
supply
current as a function of data rate for ADuM1310/ADuM1311
channel configurations.
