AN-825

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Figure 5 illustrates how an iCoupler output reacts during

various power supply states. Indeterminate operation exists

having supply rise times >0.1 V/μs. In the case where

unpowered outputs or inputs are connected to other circuits

that are powered, ensure that voltages applied to the iCoupler

are kept within the absolute maximum ratings.

STATE 3

STATE 2

STATE 1

STATE 0

OUTPUT SUPPLY

INPUT SUPPLY

INDETERMINATE

(LOGIC LOW)

FULLY OPERATIONAL

2.7V

1.8V

2.7V

Figure 5. iCoupler Output During Various Power Supply States

The key points taken from this example:

•

Rise times for supplies should be >0.1 V/μs.

•

In unpowered states, voltages applied to the iCoupler

should not exceed absolute maximum ratings.

The ADuM3xxx series of iCouplers are ESD-hardened products

that carry the same functional specifications as the ADuM1xxx

series of iCouplers. While the ADuM3xxx series was developed

to provide more robust ESD/latch-up immunity, it also

addresses the power-up and power-down problems. The

ADuM3xxx series does this with under-voltage lockout

circuitry that eliminates indeterminate operation at all supply

voltages. Use of the ADuM3xxx series should be considered in

applications where:

•

Supply rise times are <0.1 V/μs.

•

Supplies are excessively noisy.

•

Problems occur with latch-up and EOS/ESD during

system-level testing.

CALCULATING SUPPLY CURRENTS

Supply currents for iCoupler are impacted by the values of

supply voltage, output load, and data rate of the isolation

calculations for each channel and summing the results. To

iCouplers, a design tool is provided on the Analog Devices

website at www.analog.com/iCoupler.

using Equation 1 and Equation 21.

(1)

(2)

where:

per channel (mA/Mbps).

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

signaling).

currents (mA).

use the following equations: