9.1 Application Information

The ISO1500 device is designed for bidirectional data transfer on multipoint RS-485 networks. The design of each RS-485 node in the network requires an ISO1500 device and an isolated power supply as shown in Figure 32.

An RS-485 bus has multiple transceivers that connect in parallel to a bus cable. Both cable ends are terminated with a termination resistor, R_T, to remove line reflections. The value of R_T matches the characteristic impedance, Z₀, of the cable. This method, known as parallel termination, lets higher data rates be used over a longer cable length.

In half-duplex implementation, as shown in Figure 31, the driver and receiver enable pins let any node at any given moment be configured in either transmit or receive mode which decreases cable requirements.

Figure 31. Half-Duplex Network Circuit