ADUM1310_08 Datasheet, PDF (19/24 Pages) Analog Devices – Triple-Channel Digital Isolators

ADuM1310/ADuM1311
100
10
1
0.1
0.01
0.001
1k
10k
100k
1M
10M
MAGNETIC FIELD FREQUENCY (Hz)
100M
Figure 15. Maximum Allowable External Magnetic Flux Density
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 occurred during a transmitted pulse
(and had the worst-case polarity), it would reduce 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 from the
ADuM131x transformers. Figure 16 expresses these allowable
current magnitudes as a function of frequency for selected
distances. As shown, the ADuM131x is extremely immune and
can be affected only by extremely large currents operated at
high frequency very close to the component. For the 1 MHz
example noted, a 0.5 kA current would have to be placed 5 mm
away from the ADuM131x to affect the component’s operation.
1000
DISTANCE = 1m
100
10
DISTANCE = 100mm
1
DISTANCE = 5mm
0.1
0.01
1k
10k
100k
1M
10M
MAGNETIC FIELD FREQUENCY (Hz)
Figure 16. Maximum Allowable Current
for Various Current-to-ADuM131x Spacings
100M
Note that, at combinations of strong magnetic field and high
frequency, any loops formed by printed circuit board traces can
induce error voltages sufficient to trigger 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 ADuM131x
isolator is a function of the supply voltage, the channel data rate,
and the channel output load.
For each input channel, the supply current is given by
IDDI = IDDI (Q)
f ≤ 0.5 fr
IDDI = IDDI (D) × (2f − fr) + IDDI (Q)
f > 0.5 fr
For each output channel, the supply current is given by
IDDO = IDDO (Q)
f ≤ 0.5 fr
IDDO = (IDDO (D) + (0.5 × 10^−3) × CL × VDDO) × (2f − fr) + IDDO (Q)
f > 0.5 fr
where:
IDDI (D), IDDO (D) are the input and output dynamic supply currents
per channel (mA/Mbps).
CL is the output load capacitance (pF).
VDDO is the output supply voltage (V).
f is the input logic signal frequency (MHz); it is half the input
data rate, expressed in units of Mbps.
fr is the input stage refresh rate (Mbps).
IDDI (Q), IDDO (Q) are the specified input and output quiescent
supply currents (mA).
To calculate the total VDD1 and VDD2 supply current, the supply
currents for each input and output channel corresponding to
VDD1 and VDD2 are calculated and totaled. The ADuM131x
contains an internal data channel that is not available to the
user. This channel is in the same orientation as Channel A and
consumes quiescent current. The contribution of this channel
must be included in the total quiescent current calculation for
each supply. Figure 6 and Figure 7 show per-channel supply
currents as a function of data rate for an unloaded output
condition. Figure 8 shows per-channel supply current as a
function of data rate for a 15 pF output condition. Figure 9
through Figure 12 show total VDD1 and VDD2 supply current as a
function of data rate for ADuM1310/ADuM1311 channel
configurations.
INSULATION LIFETIME
All insulation structures eventually break down when subjected
to voltage stress over a sufficiently long period. The rate of
insulation degradation is dependent on the characteristics of the
voltage waveform applied across the insulation. In addition to
the testing performed by the regulatory agencies, Analog
Devices carries out an extensive set of evaluations to determine
the lifetime of the insulation structure within the ADuM131x.
Analog Devices performs accelerated life testing using voltage
levels higher than the rated continuous working voltage.
Acceleration factors for several operating conditions are
determined. These factors allow calculation of the time to
failure at the actual working voltage. The values shown in Table 10
summarize the peak voltage for 50 years of service life for a
bipolar ac operating condition and the maximum CSA/VDE
Rev. G | Page 19 of 24