• State TI Thinks Resolved
  • Locked Locked
  • Replies 5 replies
  • Answers 3 answers
  • Subscribers 33 subscribers
  • Views 2167 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.

SN65HVD232: Dead parts blocking the CAN bus interface - no reason found

David Aparisi99
Prodigy 30 points
Part Number: SN65HVD232
Other Parts Discussed in Thread: SN65HVD231, SN65HVD230

Good morning,

We have been testing several CAN nodes using the SN65HVD232. These guys interface with a 5V CAN master, and we were pretty happy until some deaths occurred.

Basically, the CAN nodes are blocking the whole line. Sorry, we ddint had the chance yet to scope the signals, because these units are being tested on a customer ... but once he replaced ONLY

the transceiver SN65HVD232 from one of the nodes (with a new one), the node started working properly again... so looks like the uC was not messing the bus, but the transceiver.

Here are some questions, until we get the hardware into our lab:

-The system uses 24VDC as main supply. We don't think there was a short between +24 and CANH/L lines, could this be a key point to find the origin of the problem? SN65HVD232 is not 24VDC tolerant ... However, only some units were damaged, a short should cause a permanent damage on all nodes ...

-Working with 5V can transceiver should not be a problem right?

-What could be the causes to make SN65HVD232 become a CANbus blocker?

-The uC in the nodes with the SN65HVD232 is 3V3 powered.

-Protections such as PESD1CAN and serial resistors between D/R and the uC are into the design.

Thanks so much for your help.

  • 0
    TI__Guru 60242 points
    David,

    -Yes, you are correct, a short on CANH and CANL should indeed affect all nodes and cause damage, however, if the short was only temporary, some devices may have survived while others were destroyed. This device can tolerate pulses of 25V on either CANH or CANL for short durations (15us). Part to part variation might make that tolerance a little bit less or a little bit more. All that being said, this doesn't sound very likely, but something to be checked.

    -A 5V CAN master shouldn't damage devices, and the input thresholds allow for the transceivers to work with a 3.3V or 5V master (they're designed this way)

    -As you stated before, a damaged device will hold the whole bus dominant, and because these devices don't have dominant timeout, this will persist until the device is removed. If the other transceivers have to drive a high on a bus that's held to GND, this could be causing damage on those transceivers as well by causing them to hit overcurrent for an extended period of time.

    Pinning down what is causing the failure will be a bit difficult until we have some waveforms, a schematic, or some other test results. If you can get any more information on the signature of the failures, that would help as well. And verifying that the parts are indeed damaged is important as well.

    Regards,
  • 0 in reply to Eric Hackett
    Prodigy 30 points

    Hi Eric,

    -24VDC is closely routed to CANH/L, but its unlikely indeed a short... Anyway, we might upgrade in next revision to a >24VDC tolerant interface, in case that could help.

    -I will get a damaged unit in next days, so we can perform any tests to reveal where was the problem.

    I attach the schematic:

    R1 is NP, and R12/R13 go straight to the uC. CAN is running at 1mbps.

    Any help is welcome,

    Thanks.

    David.

  • 0 in reply to David Aparisi99
    TI__Guru 60242 points
    David,

    Which version of the device does the customer have? SN65HVD230, SN65HVD231, or SN65HVD232? There's an internal pull up on the Rs pin, and when that pin is high, the device is either in Standby or Sleep mode. So if R1 is floating, the pin will be pulled up internally and set to that state.

    Regards,
  • 0 in reply to Eric Hackett
    Prodigy 30 points
    Hi Eric,

    It's SN65HVD232, that's fine with R1 floating right?

    Regards, David.
  • 0 in reply to David Aparisi99
    TI__Guru 60242 points
    Yes, that pin has no effect on the SN65HVD232.

    Regards,