7 Detailed Description

7.1 Overview

The ISO7840 device uses 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 EN pin is low

then the output goes to high impedance. The ISO7840 device also incorporates advanced circuit techniques to

maximize the CMTI performance and minimize the radiated emissions because of the high-frequency carrier and

IO buffer switching. The conceptual block diagram of a digital capacitive isolator, Figure 7-1, shows a functional

block diagram of a typical channel.

7.2 Functional Block Diagram

TX IN

Oscillator

OOK

Modulation

Transmitter

Emissions

Reduction

Techniques

TX Signal

Conditioning

Envelope

Detection

RX Signal

Conditioning

Receiver

EN

RX OUT

SiO2 based

Capacitive

Isolation

Barrier

Copyright © 2016, Texas Instruments Incorporated

Figure 7-1. Conceptual Block Diagram of a Digital Capacitive Isolator

Figure 7-2 shows a conceptual detail of how the ON-OFF keying scheme works.

TX IN

RX OUT

Carrier signal through

isolation barrier

Figure 7-2. On-Off Keying (OOK) Based Modulation Scheme

ISO7840, ISO7840F

SLLSEN2C – JULY 2015 – REVISED JULY 2025

www.ti.com

18

Submit Document Feedback

Copyright © 2025 Texas Instruments Incorporated

Product Folder Links: ISO7840 ISO7840F