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Part Number: ISO1050
We now use ISO1050DUBR, there's a risk of short circuit between CANL and 24Vdc(system power supply).
Base on this, I made a test like that: When system on communicated, I shorted 24Vdc power to CANL pin, keeps 5 seconds, then disconnected keeps 5 seconds; repeat shorted and disconnected; after 5-6 times like that, communication interrupted. IC CANL impedance GND2 is about 100 ohms.
then, this is my doubt: ISO1050DUBR bus fault voltage is -27~40V; how can I understand this value? why I add 24Vdc on CANL will damage the IC.
thanks for your attention, and wait for you.
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In reply to Abhi Aarey:
Wanted to add on to what Abhi has said here. As he mentioned, a block diagram would be helpful.
It looks like you are able to induce damage to side 2 of the ISO1050DUB. You are correct, that the absolute max for the CANH and CANL pins is -27 to +40V, so at first glance it is an unexpected result that you were able to damage the device with 24V. However, there are a few possibilities.
Are you transmitting on the CAN bus during this fault event (24V shorted to CANL)? One thing to note, is that while the abs max rating for CANH, CANL is -27V to +40V, damage could still occur if there is too much current. Note that the short circuit current limit is only defined for the recommended operating conditions,-12V to +12V. See section 6.6 of the ISO1050 datasheet (page 7). Relevant section pasted below:
If the ISO1050 is trying to drive a dominant on the bus while CANL is shorted to 24V, this could lead to quite a fair bit of current inside the device. Perhaps if this fault condition was held for a long duration for a higher current we could damage the driver and therefore see 100 ohms between CANL and GND2.
Abhi mentioned that the ISO1042 has an extended abs max range. It also has an extended short-circuit current limit on CANL from -5V to +40V which would easily cover your 24V. See section 6.10 of the ISO1042 datasheet (page 10). Relevant section pasted below:
For a new design, I would recommend you switch to the ISO1042DWV as I think it would be much better suited to deal with this fault condition.
In reply to Dan Kisling:
I haven't heard from you in a few days. Were you resolve your issue with ISO1050?
Thanks for your detailed explanation. We understood it now.
And, will test ISO1042-Q1 on next step; a little pity, it's not a p2p part with ISO1050.
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