3. Functional Description

3.1 Theory of Operation

The Si88xx family of products is capable of transmitting and receiving digital data signals from an isolated power domain to a local

system power domain with up to 5 kV of isolation. Each part has four unidirectional digital isolation channels. In addition, Si88xx

products include an integrated controller and switches for a dc-dc converter which regulates output voltage by sensing it on the isolated

side.

3.2 Digital Isolation

The operation of an Si88xx digital channel is analogous to that of a digital buffer, except an RF carrier transmits data across the

isolation barrier. This simple architecture provides a robust isolated data path and requires no special considerations or initialization at

start-up. A simplified block diagram for a single Si88xx channel is shown in the following figure.

RF

OSCILLATOR

MODULATOR

DEMODULATOR

A

B

Semiconductor -

Based Isolation

Barrier

Transmitter

Receiver

Figure 3.1. Simplified Si88xx Channel Diagram

A channel consists of an RF Transmitter and RF Receiver separated by a silicon dioxide capacitive isolation barrier. In the transmitter,

input A modulates the carrier provided by an RF oscillator using on/off keying. The receiver contains a demodulator that decodes the

input state according to its RF energy content and applies the result to output B via the output driver. This RF on/off keying scheme is

superior to pulse code schemes as it provides best-in-class noise immunity, low power consumption, and better immunity to magnetic

fields. See Figure 3.2 Modulation Scheme on page 7 for more details.

Input Signal

Output Signal

Modulation Signal

Figure 3.2. Modulation Scheme

Si88x4x Data Sheet • Functional Description

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com

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206332A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice • July 26, 2022

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