ADuM1400/ADuM1401/ADuM1402
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 were to occur during a transmitted
pulse (and was of 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.
POWER CONSUMPTION
The supply current at a given channel of the ADuM140x isola-
tor is a function of the supply voltage, the channel’s data rate,
and the channel’s output load.
For each input channel, the supply current is given by
I
I
DDI = IDDI (Q)
f ≤ 0.5fr
f > 0.5fr
DDI = IDDI (D) × (2f – fr) + IDDI (Q)
The preceding magnetic flux density values correspond to specific
current magnitudes at given distances from the ADuM140x trans-
formers. Figure 20 expresses these allowable current magnitudes as
a function of frequency for selected distances. As seen, the
ADuM140x is extremely immune and can be affected only by ex-
tremely large currents operated at 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 ADuM140x to affect the
component’s operation.
For each output channel, the supply current is given by
IDDO = IDDO (Q) f ≤ 0.5fr
I
DDO = (IDDO (D) + (0.5 × 10−3) × CLVDDO) × (2f – fr) + IDDO (Q)
f > 0.5fr
where:
1000.00
I
DDI (D), IDDO (D) are the input and output dynamic supply currents
DISTANCE = 1m
per channel (mA/Mbps).
100.00
CL is output load capacitance (pF).
V
DDO is the output supply voltage (V).
10.00
DISTANCE = 100mm
f is the input logic signal frequency (MHz, half of the input data
1.00
rate, NRZ signaling).
DISTANCE = 5mm
fr is the input stage refresh rate (Mbps).
0.10
0.01
I
DDI (Q), IDDO (Q) are the specified input and output quiescent sup-
ply currents (mA).
1k
10k
100k
1M
10M
100M
MAGNETIC FIELD FREQUENCY (Hz)
To calculate the total IDD1 and IDD2 supply current, the supply
currents for each input and output channel corresponding to
IDD1 and IDD2 are calculated and totaled. Figure 8 and Figure 9
provide per-channel supply currents as a function of data rate
for an unloaded output condition. Figure 10 provides per-
channel supply current as a function of data rate for a 15 pF
output condition. Figure 11 through Figure 14 provide total
IDD1 and IDD2 supply current as a function of data rate for
ADuM1400/ADuM1401/ADuM1402 channel configurations.
Figure 20. Maximum Allowable Current
for Various Current-to-ADuM140x Spacings
Note that at combinations of strong magnetic field and high
frequency, any loops formed by printed circuit board traces
could induce sufficiently large error voltages to trigger the
thresholds of succeeding circuitry. Care should be taken in the
layout of such traces to avoid this possibility.
Rev. B | Page 20 of 24
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