Why so much isolation for comms channels?

[cupoftea]

Hi,
I am just trying to jam stuff onto a PCB…..strangely, I find a lot of the room is taken up by a 7mm isolation barrier (this is a second isolation barrier). This isolation barrier exists between two areas of the board which have comms channels on them.

Call them “Area A” and “Area B”

The thing is, Area A is already an isolated secondary of an offline SMPS…which already has the 6.5mm of clearance from primary to secondary (the full “reinforced insulation”). So I am baffled as to why another 7mm isolation barrier is needed between Area A and Area B?

Area A has eight , “shall we say”, slow Comms channels on them…some 1kHz. Area B has a CAN bus going to and from it, and also, some user pushbutton controls, and an LCD display.

What circumstances may require these two wide isolation barriers?

The equipment is just for general commercial office useage.

 

[nataliarelish]

There are so many reasons for the isolation of communication channels. Isolation can enhance system reliability.

 

[KlausST]

Hi,

a lot of text. confusing. I gives me no idea of the situation on your PCB.
A simple sketch would be way more helpful.

What circumstances may require these two wide isolation barriers?

You talk about 7mm barrier. This usually is the safety barrier between mains (230V AC) and the application power area (SELV).

Whether you need a new big barrier depends on:
* the voltage you want to protect against
* and whether it is functional isolation or safety isolation.
Should be nothing new to you!

Klaus