Hi,
I have RS485 communication circuit as shown in figure. But it has no isolation, only SM712 is used for ESD protection. Now, i think it will be better to isolate the it.So, how can i isolate it? so, should i replace the RS485 (SN65HVD20D) by a internally isolated RS 485 or have to use some isolators in the circuit to isolate it?
If I use a bi-directional digital isolator (say ISO1540), can it possible to isolate the bus side A and B? Can I exactlty want to know what would be the problem if I do so? Please go through the block diagram below:
Best Answer
You can isolate the lines going to the transceiver, or you can isolate the RS-485.
Isolated transceiver:
Isolator + Transceiver:
Typically there is less choice in bus-to-bus isolators or combined transceiver/isolator chips, thus I commonly isolate CAN bus with abundant generic logic isolators and a separate transceiver, bonus point is BOM re-use. There seems to be more available for RS-485 though.
However, if you're not looking for low maintenance longevity, the isolated transceiver should be fine.
Image sources:
https://forums.parallax.com/discussion/162277/isolated-rs-485 https://www.radiolocman.com/review/article.html?di=336193
This is how the isolator work when you do not use old school optocouplers.