RS-485 - Who says you can't teach an old dog new tricks?

RS-485 - Who says you can't teach an old dog new tricks?

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Would you agree that RS-485 has turned out to be one of the most versatile communication standards when it comes to industrial applications? It’s very reliable for long distance communication and very popular. In all the years that the RS-485 standard has been around, RS-485 transceivers have undergone a lot of changes. Just like we crave more "apps" on our phones, RS-485 users want more features in the transceivers making it safer and robust.

With safety and protection in the forefront for industrial applications, transceivers today have a bunch of safety features packed into the same package. If you fear the common-mode voltage in your system is going to violate the standard (-7 to 12V), then simply choose one that has two times wider common mode range, such as the SN65HVDHVD20. By the way, we call these SUPER-485 devices because they are the true super-stars when it comes to industrial applications/harsh environments where there is likelihood of ground movement.

For cases when there is a possibility of over-voltage faults due to accidental shorting of wires to power supplies or mis-wiring, one could use transceivers, such as the SN65HVD1780, which are high-voltage fault protected. As long as the voltage on the bus lines in not greater than 70V, the device will survive. Once the fault is corrected, the system will work as expected.

Lastly, if there is clutter on the board surrounding the transceivers such as ESD diodes or transient voltage suppression (TVS) diodes, why not clean them up with the SN65HVD72 family or the SN65LBC184 devices? These devices, especially the SN65LBC184, will ensure that a lightning strike does not damage your transceiver. Yeah, it's that robust; we call it our SUPER-DUPER485.
 
Oh!! Did I mention each of these transceivers is backward compatible to the basic RS-485 transceiver without any frills? So upgrading your old solution should be as easy as hitting the easy button at Staples. Well, maybe not, but as easy as un-soldering the old device and soldering in one of these super-stars. Then watch your old RS-485 system breathe a new robust life.

  • Very exciting product line. Does TI have an isolated RS-485 device? In low power applications, does the SN65HVDHVD20 replace the need for isolation?

  • Bonnie, Yes. TI has Isolated RS485: ISO3082 family for 5V RS485 and ISO15/ISO35 for 3.3V RS485.

    SN65HVD20 does help when the ground movement is less than 25V and eliminates the need for isolation.