2. Functional Description

2.1 Theory of Operation

The operation of an Si865x channel is analogous to that of an opto coupler, except an RF carrier is modulated instead of light. 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 Si865x channel is shown in the figure below.

RF

OSCILLATOR

MODULATOR

DEMODULATOR

A

B

Semiconductor-

Based Isolation

Barrier

Transmitter

Receiver

Figure 2.1. Simplified Channel Diagram

A channel consists of an RF Transmitter and RF Receiver separated by a semiconductor-based isolation barrier. Referring to 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 the figure below for more details.

Input Signal

Output Signal

Modulation Signal

Figure 2.2. Modulation Scheme

Si8650/51/52/55 Data Sheet

Functional Description

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