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TCAN334G: Possibility of latent failures?

Josh Pieper
Prodigy 40 points
Part Number: TCAN334G

I have a system deployed with a customer that uses TCAN334Gs for all nodes in the bus.  They had an incident where 32V was shorted somewhere it shouldn't and not-surprisingly a number of the TCAN334Gs failed, but not all of them.  They continued operating the system after replacing the not-working 334Gs.  Despite no obvious problems from that point in terms of ESD or DC voltage problems, a number of the transceivers that survived the initial event failed, and new transceivers that were on the bus with them failed too.  All of the failures manifest as low resistance paths between one of CANL or CANH to ground or VCC.

I have two questions:

1. How likely is a transceiver to fail days or weeks after an over-voltage event?

2. Is there any plausible mechanism whereby such a delayed failure could cause other new transceivers on the bus to also fail?

This particular customer doesn't believe that they have had any user initiated problems since that first transient, but we are trying to figure out if there are actually ongoing ESD or other problems, or if we instead need to simultaneously replace all transceivers in the system.

In this case there are 4 buses, each with 4 nodes.  Each bus is approximately 0.5m long.  This particular customer only has one end of each bus terminated.  There are no ESD protection diodes on the CAN lines, although in this application, other than incidents with high DC voltages being applied to the CAN lines, no failures have been observed in several hundred deployments.

Thanks!

  • 0
    TI__Guru 50115 points

    Hi Josh,

    And welcome to E2E! 

    It's definitely possible that exposure to conditions outside the maximum allowed specifications could cause some damage to the device while other aspects remain functional. In this case, it sounds like the transceiver functionality remains operational, though it's possible that the internal protection circuit has been damaged by the over-voltage event. In such a case it's possible that a delay failure occurs, but I would not expect normal operation to cause this. I suspect another over-voltage event - or similar condition that would cause the protection circuitry to engage - may cause more noticeable damage due to the previous stresses. If this sounds like it would impact end-equipment reliability in a significant way, it may be prudent to replace all stressed devices. 

    I'm not sure if I understood you initial description correctly. Has this scenario seen devices that have experienced a delayed failure? Or is this a hypothetical concern? If it is the former, we may want to open another channel to discover more about the failure conditions and analyze the affected devices. If it is the latter, I hope my above explanation is helpful towards your decision.

    Regards,
    Eric Schott 

  • 0 in reply to Eric Schott1
    Prodigy 40 points

    Thanks for your reply!

    A scenario has occurred, but I am not certain that it was a delayed failure, which is why I posted.  There was no obvious source of additional stress, but the units were not in my care so I can't be sure.

    I think the answer in this case will be to replace all the stressed devices.  I'll come back if it further information presents itself.