RS-485 Transceivers for Fast Data Rates Over Long Cables

Motion control systems are requiring more accuracy over longer distances, so a key design challenge is enabling robust communications with faster data rates and longer cables. The RS-485 standard has been used for motion control because it’s a fairly high-speed interface. However, the trend is moving toward faster data rates over longer cables. For example, to increase the accuracy and efficiency of a production site, you can transfer more accurate information faster due to the higher data rate. Longer cables are  good because you have motor encoders that go up and down a system, so you need a means to communicate over long distance.

Based on these requirements, the market for communication interfaces is evolving. Some are looking to Ethernet and LVDS to accommodate faster data rates. Ethernet is expensive, however, and LVDS has not proven to be robust enough given the harsh environmental conditions under which industrial applications operation. Maxim, on the other hand, has found a way to push the boundaries of RS-485 to deliver higher performance over longer cables.

The MAX22500E (half-duplex), MAX22501E (half-duplex), and MAX22502E (full-duplex) RS-485 /RS-422 transceivers deliver 2x faster data rates and up to 50% extended cable length for motion control and industrial applications by extending the reach of communication up to 100Mbps over 50m. These specs are the industry’s fastest data rates for accurate, cost-effective, and robust communications across long cables. The chips have a settable pre-emphasis feature, which amplifies the signal from the driver’s side to allow a bigger signal to travel over long distances. As a result, the MAX22500E and MAX22502E provide 2x faster data rates versus competitive solutions for increased encoder resolution and reduced latency. The pre-emphasis capability extends cables up to 50% longer and saves up to 50% of cable costs compared with cat5E and cat6. Learn more about the advantages of having pre-emphasis in the application note, “Preemphasis Improves RS-485 Communications.”

These parts include protection features such as ±15V common mode range, ±15kV electrostatic discharge (ESD) protection (human body model), and short-circuit protected driver outputs, further increasing communications robustness.

You can integrate the parts into your existing cabling and motor control infrastructure. They’re also suited for applications such as industrial control systems, backplane busses, encoder interfaces, and field bus networks. The ICs are available in 3mm x 3mm TDFN packages, reducing overall solution footprint. Evaluation kits are available for MAX22501E and MAX22500E.

Industrial control systems in automated factories are among the applications that can benefit from higher performance RS-485 transceivers.