• State
  • Locked Locked
  • Replies 5 replies
  • Subscribers 32 subscribers
  • Views 1661 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TCAN337: Failure Mode: Low Impedance Between CAN_H and Ground and Between CAN_L and Ground

Joshua kay
Prodigy 30 points
Part Number: TCAN337

Hi,

I am using multiple TCAN337 ICs for a CAN bus with many nodes in my design. Every once in a while I notice the CAN transceivers stop working. Whenever this occurs, I can measure a low impedance (close to 0 ohms) between the CAN_H pin and ground and the CAN_L pin and ground. The IC always breaks in this manner regardless of the CAN node. After various unsuccessful attempts to recreate this failure mode, the suspicion turned to ESD as each CAN node is exposed outside of it's chassis through a connector. I added ESD protection diodes and did not see the problem for 3 weeks after seeing the problem a few times a day prior to the ESD diodes. However, the problem occurred again after adding ESD protection. Are there any vulnerabilities this particular IC has that would lead to this behavior?

Thanks,

Josh

  • 0
    TI__Guru 62910 points
    Hi Josh,

    It could still be ESD-related; e.g., maybe the TVS is protecting against most strikes but some of the harsher ones are still resulting in overvoltages at the transceiver. Another common cause of these kinds of failures is a short-circuit to a higher voltage (e.g., a DC power rail, etc.) that results in violations of a device's absolute maximum pin voltage ratings (+/-14 V for the CANH/CANL pins of TCAN337).

    Are there any sort of operational conditions that correlate to the failures? For example, do the failures occur randomly in time or do they tend to occur at system start-up or when a signal cable is connected?

    Regards,
    Max
  • 0 in reply to Miguel Robertson
    Prodigy 30 points
    Hi Max,

    Before the TVS diodes were added to the system, failures occurred quite randomly. Since TVS diodes were added, the CAN has died once (so far.) There is no noticeable pattern. However, one more data point to note is that with this most recent failure all CAN transceivers on the bus (3 nodes) failed. Although I don't know for sure if they all failed spontaneously or sequentially.

    Thanks,
    Josh
  • 0 in reply to Joshua kay
    TI__Guru 62910 points
    Josh,

    Thanks for the extra info. It's always tough to try to figure out potential causes of damage after the fact, especially if the failure rates are low and not obviously correlated to anything in particular. Since all the transceivers on the bus were damaged, my guess is that there was some kind of large overstress that exceeded the capabilities of even a TVS-protected node. Unfortunately, that is just speculation - it would be difficult to confirm.

    If you would like to send me the TVS part number I could review its datasheet to confirm that it pairs well with TCAN33x.

    Max
  • 0 in reply to Miguel Robertson
    Prodigy 30 points

    Max,

    The part number for the TVS diode is PESD2CAN,215. Additionally, the diodes are tied to the chassis of each node.

    Josh

  • 0 in reply to Joshua kay
    TI__Guru 62910 points
    That TVS is intended for higher-voltage CAN transceivers; it will not begin to clamp until above 24 V (the maximum reverse working voltage) and will clamp to a peak voltage of 41 V (for a 5-A transient). This pairs well with some other CAN transceivers (absolute maximum voltage ratings of 42-V or higher are common for automotive transceivers), but does not provide much protection for the TCAN33x (which has a much smaller absolute maximum range). Something with a working voltage in the ~10-12 V range would probably be more appropriate (e.g., MMBZ10V/MMBZ12V).

    Max