SI8751 Datasheet, PDF (4/27 Pages) Silicon Laboratories – Digital CMOS input option

Si8751/52 Data Sheet
System Overview
The operation of an Si875x channel is analogous to that of an optocoupler and gate driver, 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 Si875x channel is shown in the figure below.
Transmitter
Receiver
A
MODULATOR
Semiconductor-
Based Isolation
DEMODULATOR
B
Barrier
RF OSCILLATOR
Figure 2.3. 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 Figure 2.4 Modulation Scheme on page 3 for more details.
Input Signal
Modulation Signal
Output Signal
Figure 2.4. Modulation Scheme
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