ADM2682EBRIZ Analog Devices Inc, ADM2682EBRIZ Datasheet - Page 17

• Manufacturer Part Number: ADM2682EBRIZ
• Description: 58T8844
• Manufacturer: Analog Devices Inc

Specifications of ADM2682EBRIZ

• No. Of Channels: 1
• Propagation Delay: 100ns
• Supply Current: 175mA
• Supply Voltage Range: 3V To 5.5V
• Digital Ic Case Style: SOIC
• No. Of Pins: 16
• Operating Temperature Range: -40°C To +85°C
• Rohs Compliant: Yes

is assumed to be unpowered or nonfunctional, in which case,
the isolator output is forced to a default state by the watchdog
timer circuit.
This situation should occur in the
only during power-up and power-down operations. The limitation
on the
by the condition in which induced voltage in the transformer
receiving coil is sufficiently large to either falsely set or reset the
decoder. The following analysis defines the conditions under
which this can occur.
The 3.3 V operating condition of the
is examined because it represents the most susceptible mode of
operation. The pulses at the transformer output have an amplitude
of >1.0 V. The decoder has a sensing threshold of about 0.5 V,
thus establishing a 0.5 V margin in which induced voltages can
be tolerated. The voltage induced across the receiving coil is
given by
where:
β is magnetic flux density (gauss).
N is the number of turns in the receiving coil.
r
Given the geometry of the receiving coil in the ADM2682E/
ADM2687E
voltage be, at most, 50% of the 0.5 V margin at the decoder, a
maximum allowable magnetic field is calculated as shown in
Figure 39.
n
is the radius of the n
0.001
V = (−dβ/dt)Σπr
0.01
100
Figure 39. Maximum Allowable External Magnetic Flux Density
0.1
10
ADM2682E/ADM2687E
1
1k
and an imposed requirement that the induced
10k
MAGNETIC FIELD FREQUENCY (Hz)
n
2
th
; n = 1, 2, … , N
turn in the receiving coil (cm).
100k
magnetic field immunity is set
ADM2682E/ADM2687E
1M
ADM2682E/ADM2687E
10M
100M
devices
Rev. 0 | Page 17 of 24
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 of the worst-case polarity), it reduces the received pulse
from >1.0 V to 0.75 V, which 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 from the
ADM2682E/ADM2687E
these allowable current magnitudes as a function of frequency
for selected distances. As shown in Figure 40, the ADM2682E/
ADM2687E
extremely large currents operated at high frequency very close
to the component. For the 1 MHz example, a 0.5 kA current must
be placed 5 mm away from the
component operation.
Note that in combinations of strong magnetic field and high
frequency, any loops formed by PCB traces can induce error
voltages sufficiently large to trigger the thresholds of succeeding
circuitry. Take care in the layout of such traces to avoid this
possibility.
0.01
100
Figure 40. Maximum Allowable Current for Various Current-to-
0.1
1k
10
1
1k
DISTANCE = 100mm
are extremely immune and can be affected only by
10k
ADM2682E/ADM2687E
DISTANCE = 5mm
MAGNETIC FIELD FREQUENCY (Hz)
transformers. Figure 40 expresses
100k
ADM2682E/ADM2687E
ADM2682E/ADM2687E
1M
Spacings
DISTANCE = 1m
10M
100M
to affect