8 Detailed Description

8.1 Overview

The ISO674x family of devices have an ON-OFF keying (OOK) modulation scheme to transmit the digital data

across a silicon dioxide based isolation barrier. The transmitter sends a high frequency carrier across the barrier

to represent one digital state and sends no signal to represent the other digital state. The receiver demodulates

the signal after advanced signal conditioning and produces the output through a buffer stage. If the ENx pin is

low then the output goes to high impedance. The ISO674x devices also incorporate advanced circuit techniques

to maximize the CMTI performance and minimize the radiated emissions due to the high frequency carrier and

IO buffer switching. The conceptual block diagram of a digital capacitive isolator, Figure 8-1, shows a functional

block diagram of a typical channel.

8.2 Functional Block Diagram

TX IN

Oscillator

OOK

Modulation

Transmitter

Emissions

Reduction

Techniques

TX Signal

Conditioning

Envelope

Detection

RX Signal

Conditioning

Receiver

EN

RX OUT

Capacitive

Isolation

Barrier

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Figure 8-1. Conceptual Block Diagram of a Digital Capacitive Isolator

Figure 8-2 shows a conceptual detail of how the ON-OFF keying scheme works.

TX IN

RX OUT

Carrier signal through

isolation barrier

Figure 8-2. On-Off Keying (OOK) Based Modulation Scheme

ISO6741

SLLSFJ6A – AUGUST 2020 – REVISED OCTOBER 2020

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