TX IN

RX OUT

Carrier signal through

isolation barrier

TX IN

Oscillator

OOK

Modulation

Transmitter

Emissions

Reduction

Techniques

TX Signal

Conditioning

Envelope

Detection

RX Signal

Conditioning

Receiver

EN

RX OUT

Capacitive

Isolation

Barrier

Copyright © 2016, Texas Instruments Incorporated

17

ISO7730, ISO7731

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SLLSES0B – SEPTEMBER 2016 – REVISED OCTOBER 2016

Product Folder Links: ISO7730 ISO7731

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Copyright © 2016, Texas Instruments Incorporated

8 Detailed Description

8.1 Overview

The ISO773x family of devices has 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 ISO773x family of devices also incorporates advanced circuit

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

carrier and IO buffer switching. The conceptual block diagram of a digital capacitive isolator, Figure 17, shows a

functional block diagram of a typical channel.

8.2 Functional Block Diagram

Figure 17. Conceptual Block Diagram of a Digital Capacitive Isolator

Figure 18 shows a conceptual detail of how the ON/OFF keying scheme works.

Figure 18. On-Off Keying (OOK) Based Modulation Scheme