ADUM1400(2004) データシートの表示（PDF） - Analog Devices

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ADUM1400
(Rev.:2004)

Quad-Channel Digital Isolators

Analog Devices 

ADuM1400/ADuM1401/ADuM1402

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 were to occur during a transmitted

pulse (and was of 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 ADuM140x trans-

formers. Figure 20 expresses these allowable current magnitudes as

a function of frequency for selected distances. As seen, the

ADuM140x is extremely immune and can be affected only by ex-

tremely large currents operated at high frequency, very close to the

component. For the 1 MHz example noted, one would have to place

a 0.5 kA current 5 mm away from the ADuM140x to affect the

component’s operation.

1000.00

100.00

DISTANCE = 1m

10.00

DISTANCE = 100mm

1.00

DISTANCE = 5mm

0.10

0.01

1k

10k

100k

1M

10M

MAGNETIC FIELD FREQUENCY (Hz)

100M

Figure 20. Maximum Allowable Current

for Various Current-to-ADuM140x Spacings

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 ADuM140x isola-

tor is a function of the supply voltage, the channel’s data rate,

and the channel’s output load.

For each input channel, the supply current is given by

IDDI = IDDI (Q)

f ≤ 0.5fr

IDDI = IDDI (D) × (2f – fr) + IDDI (Q)

f > 0.5fr

For each output channel, the supply current is given by

IDDO = IDDO (Q)

f ≤ 0.5fr

IDDO = (IDDO (D) + (0.5 × 10−3) × CLVDDO) × (2f – fr) + IDDO (Q)

f > 0.5fr

where:

IDDI (D), IDDO (D) are the input and output dynamic supply currents

per channel (mA/Mbps).

CL is output load capacitance (pF).

VDDO is the output supply voltage (V).

f is the input logic signal frequency (MHz, half of the input data

rate, NRZ signaling).

fr is the input stage refresh rate (Mbps).

IDDI (Q), IDDO (Q) are the specified input and output quiescent sup-

ply currents (mA).

To calculate the total IDD1 and IDD2 supply current, the supply

currents for each input and output channel corresponding to

IDD1 and IDD2 are calculated and totaled. Figure 8 and Figure 9

provide per-channel supply currents as a function of data rate

for an unloaded output condition. Figure 10 provides per-

channel supply current as a function of data rate for a 15 pF

output condition. Figure 11 through Figure 14 provide total

IDD1 and IDD2 supply current as a function of data rate for

ADuM1400/ADuM1401/ADuM1402 channel configurations.

Rev. B | Page 20 of 24

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