Hello all,
I have recently had 3 units come across my desk which were described as 'not communicating on the CAN bus'.
These units are potted so I began by measuring R's & C's across CANHI, CANLO, GND and VCC against a reference unit. I immediately noticed that the resistance between the CAN lines and GND, and every permutation thereof, was reading below 100 ohm.
I then removed the potting to see what was causing this - I removed the input protection circuit and measured again, with the same result.
After replacing the ISO1050DUB package the unit functioned again.
I repeated this on the second unit, however this time it was just the CANHI and GND pair that exhibited a low resistance.
I verified that the power supply to each side of the transceiver was reading 5.05V and the CAN lines are protected by a dual CAN-BUS ESD protection diode and a common mode choke.
What could possibly be the cause of this and is there anything else we can incorporate into the design to prevent this from happening again?
All 3 units that have failed appear [ in removing the potting the markings were removed - but all the units were built at the same time, so components would have been off the same reel ] to be built from the same batch of ISO1050's so is it possible that this was a batch issue?
I have 2 extracted ISO1050DUB's if anyone would like to take a look also. I can extract the 3rd if necessary and try not to remove the package marking.
Many thanks.
Ryan