ADUM1310 AD [Analog Devices], ADUM1310 Datasheet - Page 13

• Manufacturer Part Number: ADUM1310
• Description: Triple-Channel Digital Isolator with Programmable Default Output
• Manufacturer: AD [Analog Devices]

Given the geometry of the receiving coil in the ADuM1310 and
an imposed requirement that the induced voltage be at most
50% of the 0.5 V margin at the decoder, a maximum allowable
magnetic field at a given frequency can be calculated. The result
is shown in Figure 11.
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 approximately
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—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 ADuM1310
transformers. Figure 12 expresses these allowable current mag-
nitudes as a function of frequency for selected distances. As
can be seen, the ADuM1310 is extremely immune and can be
affected only by extremely large currents operated at high fre-
quency, very close to the component. For the 1 MHz example
noted, a 0.5 kA current needed to be placed 5 mm away from
the ADuM1310 to affect the operation of the component.
0.001
1000
0.01
0.01
Figure 11. Maximum Allowable External Magnetic Flux Density
100
100
0.1
10
10
1
1
1
1k
1k
Figure 12. Maximum Allowable Current for Various
DISTANCE = 100mm
10k
DISTANCE = 5mm
Current-to-ADuM1310 Spacings
10k
MAGNETIC FIELD FREQUENCY (Hz)
MAGNETIC FIELD FREQUENCY (Hz)
100k
100k
1M
1M
DISTANCE = 1m
10M
10M
100M
100M
Rev. E | Page 13 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. 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 ADuM1310
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 (Hz, 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
provide per-channel supply currents as a function of the data
rate for an unloaded output condition. Figure 6 provides per-
channel supply current as a function of the data rate for a 15 pF
output condition. Figure 7 through Figure 8 provide total I
and I
ADuM1310.
r
DDI (D)
DDI (Q)
DD1
L
DDO
is the input stage refresh rate (bps).
is the output load capacitance (pF).
and I
I
I
I
I
DD2
is the output supply voltage (V).
DDI
DDI
DDO
DDO
, I
, I
DDO (D)
DDO (Q)
supply current as a function of the data rate for the
= I
= I
= I
= (I
DD2
DDI (Q)
DDI (D)
DDO (Q)
are calculated and totaled. Figure 4 and Figure 5
DDO (D)
are the input and output dynamic supply currents
are the specified input and output quiescent
× (2f – f
+ C
DD1
L
V
r
DDO
) + I
and I
) × (2f – f
DDI (Q)
DD2
supply current, the supply
r
) + I
DDO (Q)
ADuM1310
f ≤ 0.5f
f ≤ 0.5f
f ≤ 0.5f
f > 0.5f
DD1
r
r
r
r