Si8440/1/2

Rev. 0.3

15

3. Application Information

3.1. Theory of Operation

The operation of an Si8440 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 Si8440 channel is shown in

Figure 12. A channel consists of an RF transmitter and receiver separated by a transformer.

Referring to the transmitter, input A modulates the carrier provided by an RF oscillator using on/off keying and

applies the resulting waveform to the primary of the transformer. 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.

3.2. Eye Diagram

Figure 13 illustrates an eye-diagram taken on an Si8440-IS. The test used an Anritsu (MP1763C) Pulse Pattern

Generator for the data source. The output of the generator's clock and data from an Si8440-IS were captured on an

oscilloscope. The results illustrate that data integrity was maintained even at the high data rate of 150 Mbps. The

results also show that very low pulse width distortion and very little jitter were exhibited.

Figure 12. Simplified Channel Diagram

Figure 13. Eye Diagram

TRANSMITTER

RECEIVER

RF

OSCILLATOR

MODULATOR

DEMODULATOR

A

B