ADM2490E

Rev. 0 | Page 13 of 16

CIRCUIT DESCRIPTION

ELECTRICAL ISOLATION

In the ADM2490E, electrical isolation is implemented on the

logic side of the interface. Therefore, the part has two main

sections: a digital isolation section and a transceiver section

(see Figure 21). The driver input signal, which is applied to the

across an isolation barrier to appear at the transceiver section

input, which is referenced to isolated ground in the transceiver

section, is coupled across the isolation barrier to appear at the

RxD pin referenced to logic ground.

iCoupler Technology

The digital signals are transmitted across the isolation barrier

using iCoupler technology. This technique uses chip scale

transformer windings to couple the digital signals magnetically

from one side of the barrier to the other. Digital inputs are

encoded into waveforms that are capable of exciting the

primary transformer winding. At the secondary winding, the

induced waveforms are decoded into the binary value that was

originally transmitted.

TRUTH TABLES

The truth tables in this section use the abbreviations shown in

Table 10.

Table 10. Truth Table Abbreviations

Abbreviation

Description

H

High level

I

Indeterminate

L

Low level

X

Irrelevant

Table 11. Transmitting

Supply Status

Input

Outputs

TxD

Y

Z

On

On

H

H

L

On

On

L

L

H

Table 12. Receiving

Supply Status

Inputs

Output

A − B (V)

RxD

On

On

>0.2

H

On

On

<−0.2

L

On

On

−0.2 < A − B < +0.2

I

On

On

Inputs open

H

On

Off

X

H

Off

On

X

H

Off

Off

X

L

ISOLATION

BARRIER

Y

Z

A

B

TxD

RxD

ENCODE

DECODE

DECODE

ENCODE

D

R

TRANSCEIVER

DIGITAL ISOLATION

Figure 21. ADM2490E Digital Isolation and Transceiver Sections