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SN65C1168E: Communication between SN65C1168E (Tx)-ISO3086 (Rx) stops

cafain
Mastermind 6535 points
Part Number: SN65C1168E
Other Parts Discussed in Thread: ISO3086

Hi, staff

Communication between SN65C1168E (Tx)-ISO3086 (Rx) stops.
Once communication stops, it will not resume until you replace the device.
This means that the device has been corrupted for some reason.
I want to know the cause of device damage.

Circuit configuration
                              Board-A                                                                            Board-B
[SN65C1168E (10pin, 11pin) →　connector] ----440mm cable---- [connector → ISO3086(14pin, 13pin)]
SN65C1168E:Vcc=5V                                                                      ISO3086:Vcc1=3.3V, Vcc2=5.0V

SN65C1168E (10pin, 11pin) has 56Ω termination on Board-B side.
The communication signal is about 240kHz.

We confirmed that this circuit configuration can not communicate.
This bug does not occur immediately after the start, but occurs after a while after the start of use.

At the time of failure, the resistance value of the following terminals was measured.
The impedance of 10pin-8pin of SN65C1168E has dropped to 14-280ohms.
The impedance of the 11pin-8pin is also lowered to 0.9 to 166ohms.

The impedance of 13 pin-8 pin of ISO3086 has dropped to 0.6-33ohms.
The impedance of 14pin-8pin is also lowered to 0.7 to 56ohms.

It will communicate normally if you replace the device that can not communicate, but after a while
I can not communicate again.

What is this factor?

Please let us know your request for information on this bug.
best regards
cafain

  • 0
    TI__Mastermind 25705 points
    Cafain,

    I'm sorry to hear your problem. Is the issue repeatable? Can you check the grounding of board-A and board-B? Is there any potential between them? Could you re-test with the same ground? In the meantime, you can contact TI quality team to submit damaged SN65C1168E and ISO3086 parts for failure analysis.

    Regards,
    Hao
  • 0 in reply to Hao L
    Mastermind 6535 points

    HI, Hao-san


    Thank you for your urgent comments.
    Reproduction is possible.

    Because of the circuit configuration, only two signal lines are connected between Board-A and Board-B,
    and GND is not common.

    As Board-A and Board-B have their own power supply, GND is not common either.
    Is this considered the cause of the failure?

    best regards

    cafain

  • 0 in reply to cafain
    TI__Mastermind 25705 points

    Cafain-san,

    To be honest I'm not sure where the problem is. However grounding is the first thing we check for debugging. As I mentioned, if it's not convenient to check the potential difference, you could use a third wire to connect the ground on both ends to see if it helps.

    Regards,

    Hao

  • 0 in reply to Hao L
    TI__Guru 62920 points
    Hi Cafain-san,

    I just wanted to check in. Have you made in progress in debugging this issue? I agree with Hao's comment that checking the grounding would be a good first step given that this application involves independent grounds at each node.

    Max