Re: CAN Bus protection (100VDC)


PeteS wrote:
StanV wrote:
We designed a machine where we have at some place the CAN-bus signals
and HighVoltage power (100VDC and 220VAC) on the same cable.

So , we are just awaiting a faulty cable or connector to get these
voltages on the bus.

If you are making the CAN signals 'ride' on the power, then they will
have a **common mode voltage** of whatever that power is, and you'll be
hard pressed to find an IC with 311V of common mode range (the peak
voltage of 220Vac) and can withstand a similar negative excursion.
It's not just protection, it's data recovery in the presence of such
high common mode voltages that will be the problem.

I think Stan was talking about the power being on separate wires in the
same cable as the data lines and was wondering about protection against
the power lines shorting to the data lines.

I think he's going to need a fuse (maybe a polyswitch) and watch out
for the effects of the introduced capacitance and resistance. Raychem
has some telcom protection devices that might be worth looking at.

Robert

.

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