The integrated signal isolation channels employ 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 state and sends no signal to represent the other state. The receiver demodulates the signal after signal conditioning and produces the output through a buffer stage. The signal-isolation channels incorporate advanced circuit techniques to maximize the CMTI performance and minimize the radiated emissions from the high frequency carrier and IO buffer switching. Figure 10-2 shows a functional block diagram of a typical signal isolation channel.

In order to keep any noise coupling from power converter away from signal path, power supplies on side1 for power converter (V_DD) and signal path(V_IO) are kept separate. Similarly on side2, power converter output (V_ISOOUT ) needs to be connected to power supply for RS-485 (V_ISOIN) externally on PCB. For more details, refer to Layout guidelines section.