Datasheet

ADuM1300/ADuM1301 Data Sheet
Rev. K | Page 26 of 32
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 from the
ADuM1300/ADuM1301 transformers. Figure 17 shows these
allowable current magnitudes as a function of frequency for
selected distances. The ADuM1300/ADuM1301 is extremely
immune and can be affected only by extremely large currents
operated at a high frequency very close to the component. For
the 1 MHz example noted, one would have to place a 0.5 kA
current 5 mm away from the ADuM1300/ADuM1301 to affect
the operation of the component.
Figure 17. Maximum Allowable Current
for Various Current-to-ADuM1300/ADuM1301 Spacings
Note that at combinations of strong magnetic field and high
frequency, any loops formed by printed circuit board traces
could 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 ADuM1300/
ADuM1301 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).
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 of 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. 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 12
provide total V
DD1
and
V
DD2
supply current as a function of data rate for ADuM1300/
ADuM1301 channel configurations.
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
03787-018