adum3210 Analog Devices, Inc., adum3210 Datasheet - Page 16

• Manufacturer Part Number: adum3210
• Description: Dual-channel Digital Isolator, Enhanced System-level Esd Reliability
• Manufacturer: Analog Devices, Inc.

ADuM3210
The pulses at the transformer output have an amplitude greater
than 1.0 V. The decoder has a sensing threshold at about 0.5 V,
therefore 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 the magnetic flux density (gauss).
N is the number of turns in the receiving coil.
r
Given the geometry of the receiving coil in the ADuM3210
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 10.
For example, at a magnetic field frequency of 1 MHz, the maxi-
mum 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
had the worst-case polarity), it would reduce 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 away from the
ADuM3210 transformers. Figure 11 expresses these allowable
current magnitudes as a function of frequency for selected
distances. As shown, the ADuM3210 is immune and can be
affected only by extremely large currents operated at a high
frequency and very close to the component. For the 1 MHz
example, one would have to place a 0.5 kA current 5 mm away
from the ADuM3210 to affect the component’s operation.
n
is the radius of the nth turn in the receiving coil (cm).
V = (−dβ/dt) ∑π r
0.001
0.01
Figure 10. Maximum Allowable External Magnetic Flux Density
100
0.1
10
1
1k
10k
MAGNETIC FIELD FREQUENCY (Hz)
n
2
, n = 1, 2, ... , N
100k
1M
10M
100M
Rev. A | Page 16 of 20
Note that at combinations of strong magnetic fields and high
frequencies, any loops formed by PCB traces may induce
sufficiently large error voltages to trigger the threshold of
succeeding circuitry. Care should be taken in the layout of
such traces to avoid this possibility.
POWER CONSUMPTION
The supply current at a given channel of the ADuM3210
isolator is a function of the supply voltage, channel
data rate, and channel output load.
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, half of the input data
rate, NRZ signaling).
f
I
supply currents (mA).
To calculate the total I
currents for each input and output channel corresponding to
I
Figure 4 provides per-channel input supply currents as a function
of data rate. Figure 5 and Figure 6 provide per-channel output
supply currents as a function of data rate for an unloaded
output condition and for a 15 pF output condition, respectively.
Figure 7 and Figure 8 provide total I
as a function of data rate.
r
DDI (D)
DDI (Q)
DD1
L
DDO
is the input stage refresh rate (Mbps).
is the output load capacitance (pF).
and I
I
I
I
I
1000
is the output supply voltage (V).
0.01
DDI
DDI
DDO
DDO
, I
, I
100
0.1
10
DDO (D)
DDO (Q)
1
1k
= I
= I
= I
= (I
DD2
Figure 11. Maximum Allowable Current for Various
DISTANCE = 100mm
DDI (Q)
DDI (D)
DDO (Q)
are calculated and totaled.
DDO (D)
are the input and output dynamic supply currents
are the specified input and output quiescent
× (2f – f
DISTANCE = 5mm
Current-to-ADuM3210 Spacings
10k
+ (0.5 × 10
MAGNETIC FIELD FREQUENCY (Hz)
DD1
r
) + I
and I
100k
DDI (Q)
−3
DD2
) × C
supply current, the supply
DD1
L
1M
V
DDO
and I
DISTANCE = 1m
) × (2f – f
DD2
10M
supply current
r
) + I
f ≤ 0.5f
f > 0.5f
f ≤ 0.5f
f > 0.5f
100M
DDO (Q)
r
r
r
r