ad51-069-0reel Analog Devices, Inc., ad51-069-0reel Datasheet - Page 16

• Manufacturer Part Number: ad51-069-0reel
• Description: Half-duplex Icoupler-r Isolated Rs-485 Transceiver
• Manufacturer: Analog Devices, Inc.

ADM2483
Given the geometry of the receiving coil and an imposed
requirement that the induced voltage is, at most, 50% of the
0.5 V margin at the decoder, a maximum allowable magnetic
field is calculated, as shown in Figure 27.
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
is the worst-case polarity, it reduces the received pulse from
>1.0 V to 0.75 V. This is well above the 0.5 V sensing threshold
of the decoder.
These magnetic flux density values are shown in Figure 28,
using more familiar quantities such as maximum allowable
current flow, at given distances away from the ADM2483
transformers.
100.000
10.000
Figure 27. Maximum Allowable External Magnetic Flux Density
1.000
0.100
0.010
0.001
1k
10k
MAGNETIC FIELD FREQUENCY (Hz)
100k
1M
10M
100M
Rev. B | Page 16 of 20
At combinations of strong magnetic field and high frequency,
any loops formed by printed circuit board traces could induce
large enough error voltages to trigger the thresholds of
succeeding circuitry. To avoid this possibility, care should be
taken in the layout of such traces.
1000.00
100.00
10.00
1.00
0.10
0.01
1k
Figure 28. Maximum Allowable Current for Various
DISTANCE = 5mm
DISTANCE = 100mm
10k
Current-to-ADM2483 Spacings
MAGNETIC FIELD FREQUENCY (Hz)
100k
DISTANCE = 1m
1M
10M
100M