ISO1050: RX didn't receive data issue

Part Number: ISO1050

Hi Team,

My customer using ISO1050 discover a issue that RX didn't change when TX sent data.

Please see schematic and waveform as below.

Have you seen similar case?

Tiffany Liu

12 Replies

  • Hi Tiffany,

    I'm sorry to hear that you are having an issue with the ISO1050. I think this is the first time I have seen a case like this, but perhaps I do not have enough details yet. I have a few follow up questions for you:

    Is this error repeatable?

    Does this happen during startup?

    Best regards, 

    Dan

  • In reply to Dan Kisling:

    Hi Dan,
    This error can be easily reproduced and it's not just happened at startup.
    I have tried to use PCAN transmitting TX at period 1sec repeatedly and expect for receiving RX from client.
    Some expected RX didn't received from client which is correspond to the waveform shown.
    And i also find that when i heat up this ISO1050 (using hair dryer ), the fail disappear.
    But using Refrigerant, the fail phenomenon actually become worse.

  • In reply to Zhe Ming Zhuang65:

    Hi Zhe Ming,

    Thank you for providing additional details.

    What is the horizontal time division on the scope set to in the scope shot you have sent? I am trying to determine the pulse width of the bit that the ISO1050 did not transmit.

    Since it is easy to reproduce, I would like to try to recreate this in our labs. Are there any other details you can provide to best re-create this issue? I have the following details from your schematic: Vcc1 = 3.3V, Vcc2 = 5.0V, 120 Ohm termination on CAN bus, issue gets worse with cold temperatures.

    Best regards,
    Dan
  • In reply to Dan Kisling:

    Hi Dan:

    From the previous attached figure, the room factor is 2kX, so the time division should be 2k*10us=20ms (Sorry for all measured figures are zoom in setting).

    And an interest thing can be noticed that at normal condition, the CAN TX will lead RX about 120ns. But before "bit stuff error" happened, the CAN RX rise at the same time with CAN TX.

    As you know, the pin space are wide that can exclude the SMD impact. But  i will still take the photograph and X-Ray to examine at this aspect.

    Figure 1: When Stuffing error happened, you can found previous TX RX vary at the same time

    Figure 2: Zoom in Figure 1

    Figure 3: At normal condition, TX lead RX by 12X ns

    12X ns fits the IC spec.

    I trigger this fault by CAN decoder and the trigger condition is "Stuffing error".

    Could you guess the reason why TX and RX can rise at the same time ? I think this is a breakthrough point.

    Thanks for your support : )

  • In reply to Zhe Ming Zhuang65:

    Hi Zhe Ming,

    Yes after closer inspection it is very suspicious that TX and RX happen simultaneously. The ISO1050 is not capable of doing this by itself.

    How are CAN_TX and CAN_RX connected to the microcontroller? One thing I think would be worth trying is to disconnect CAN_RX from the micro and get similar scope shots as you obtained before.

    Best regards,
    Dan

  • In reply to Dan Kisling:

    Hi Dan:

    As previous schematic shows, CAN0_RX & CAN0_TX connect to MCU  CAN port directly.

    After taking the photograph, there have no found related SMD problem.

    And yes, after taking X-Ray, i will implement SWAP test of ISO1050 and this can exclude the MCU side doubt.

    By the way, previous experiment that when temp drop, the fail phenomenon happened apparently .

    At that time, i only use refrigerant toward ISO1050(only small region).

    The distance between MCU and ISO1050 is about 18cm, so the temp vary can't directly influence the CAN port of MCU.

    This make me more sure that this problem come with ISO1050.

    Ya, i think it's right that at normal ISO1050, RX and TX shouldn't rise at the same time.

    But if this ISO1050 actually failed and can reproduce this problem.

    Is there any possibility can produce this problem for reviewing ISO1050 internal design and manufacture process ?

    Bgds

    Jimmy

  • In reply to Zhe Ming Zhuang65:

    Hi Jimmy,

    Yes please continue with the experiments described. Looking further at the failure scope shot you sent earlier: RX is actually predicting the future a bit. Signal should propagate TX --> CAN --> RX. It looks like RX is actually switching before the CAN bus transitions.

    Is it possible the input of your micro controller (CAN_RX) is somehow driving the line? Perhaps the drive strength of RX on ISO1050 is stronger when the device is heated and so it is able to overcome the micro, but during cold or room temp the ISO1050 is not able to.

    Best regards,
    Dan
  • In reply to Dan Kisling:

    Hi Jimmy,
    I haven't heard from you in a few days. Were you able to resolve the RX issue?
    Best regards,
    Dan
  • In reply to Dan Kisling:

    Hi Dan:

    I will swap ISO1050 tomorrow, thanks.

  • In reply to Zhe Ming Zhuang65:

    Hi Dan:

    After swap ISO1050, the phenomenon come up with ISO1050 IC.

    And i also take X-Ray photograph of this IC, it seems bonding wires are normal.

    Later i will send this sample to TI (Taiwan) for further analysis.

    Thanks

    Jimmy