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Hello,
this question refers to ESD, EFT and surge protection in an RS-485 isolated node which cannot be connected to protective earth neither on the bus side nor on the other side. Both GND1 and GND2/GND3 are floating wrt PE. No possibility of connection of the PCB to PE. The node connects to the master through a three-wire cable (data+, data-, data common) which can extend up to 100m.
I use 3 TVS diodes: 1 between A2 and GND3, 1 between B2 and GND3 and one between A2 and B2.
My question is: is still worth using the TVS diodes on the bus side port? Or are they useless?
Thank you for the support.
Roberto