ADUM1280 AD [Analog Devices], ADUM1280 Datasheet - Page 14

• Manufacturer Part Number: ADUM1280
• Description: 3 kV RMS Dual Channel Digital Isolators
• Manufacturer: AD [Analog Devices]

ADuM1280/ADuM1281/ADuM1285/ADuM1286
For example, at a magnetic field frequency of 1 MHz, the
maximum allowable magnetic field of 0.08 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.
If such an event occurs, with the worst-case polarity, during a
transmitted pulse, it would reduce the received pulse from >1.0 V
to 0.75 V. This is 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
transformers. Figure 14 expresses these allowable current magni-
tudes as a function of frequency for selected distances. The
ADuM1280
large, high frequency currents, very close to the component
could potentially be a concern. For the 1 MHz example noted,
one would have to place a 0.2 kA current 5 mm away from the
ADuM1280
1000
0.01
100
0.1
10
1
1k
DISTANCE = 100mm
is very insensitive to external fields. Only extremely
to affect component operation.
Figure 14. Maximum Allowable Current for
10k
Various Current to
DISTANCE = 5mm
MAGNETIC FIELD FREQUENCY (Hz)
100k
ADuM1280
1M
DISTANCE = 1m
Spacings
10M
ADuM1280
100M
Rev. 0 | Page 14 of 16
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. Take care to avoid PCB
structures that form loops.
POWER CONSUMPTION
The supply current at a given channel of the
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
For each output channel, the supply current is given by
where:
I
per channel (mA/Mbps).
C
V
f is the input logic signal frequency (MHz); it is half the input
data rate, expressed in units of Mbps.
f
I
supply currents (mA).
To calculate the total V
currents for each input and output channel corresponding to
V
show per-channel supply currents as a function of data rate for
an unloaded output condition. Figure 8 shows the per-channel
supply current as a function of data rate for a 15 pF output
condition. Figure 9 through Figure 11 show the total V
V
ADuM1281
r
DDI (D)
DDI (Q)
L
DDO
is the input stage refresh rate (Mbps) = 1/t
DD1
DD2
is the output load capacitance (pF).
I
I
I
I
and V
supply current as a function of data rate for
is the output supply voltage (V).
DDO
DDI
DDI
DDO
, I
, I
DDO (D)
DDO (Q)
= I
= I
= (I
= I
DD2
DDI (Q)
DDI (D)
DDO (Q)
channel configurations.
DDO (D)
are the input and output dynamic supply currents
are the specified input and output quiescent
are calculated and totaled. Figure 6 and Figure 7
× (2f − f
+ (0.5 × 10
DD1
r
) + I
and V
−3
DDI (Q)
) × C
DD2
L
supply current, the supply
× V
DDO
) × (2f − f
r
ADuM128x
(µs).
Data Sheet
ADuM1280/
r
f ≤ 0.5 f
f > 0.5 f
f ≤ 0.5 f
f > 0.5 f
) + I
DD1
DDO (Q)
and
r
r
r
r