A good PCB layout for the MAX490EESA+T involves keeping the analog and digital grounds separate, using a solid ground plane, and placing the device close to the power supply. Additionally, using a shielded cable for the RS-485 bus and keeping the bus lines as short as possible can help minimize EMI.
To ensure reliable communication over long distances, use a twisted-pair cable, keep the cable shield connected to the GND pin of the MAX490EESA+T, and use a common-mode choke or ferrite bead to filter out high-frequency noise. Also, consider using a repeater or a fiber optic converter for very long distances.
The maximum cable length supported by the MAX490EESA+T depends on the data rate and the type of cable used. As a general rule, the maximum cable length is approximately 4000 feet (1219 meters) at a data rate of 10 Mbps, but this can be extended using repeaters or fiber optic converters.
To protect the MAX490EESA+T from electrical surges and overvoltage, use a surge protector or a transient voltage suppressor (TVS) diode on the RS-485 bus lines. Additionally, consider using a fuse or a polyfuse to limit the current in case of an overvoltage condition.
The operating temperature range of the MAX490EESA+T is -40°C to +85°C. However, the device can be operated at temperatures up to +105°C for short periods of time, but this may affect its reliability and lifespan.
MAX490EESA+T datasheet
by Maxim Integrated Products
