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TCAN1042V-Q1: CAN transceiver communication ability under "short to GND/Vbat" or "Open" condition

Kento Adachi
Expert 4555 points
Part Number: TCAN1042V-Q1

Tool/software:

Hello experts,

Customer would like to know whether TCAN1042V-Q1 can communicate under the following conditions or not.

1. CANH = OPEN, CANL = normal

2. CANH = Short to GND, CANL = normal

3. CANH = Short to Vbat, CANL = normal

4. CANH = normal, CANL = OPEN

5. CANH = normal, CANL = Short to GND

6. CANH = normal, CANL = Short to Vbat

I think every condition does not work because we cannot appropriately judge dominant/recessive state, but could you please let me know the answers?

Thanks,

Kento

  • 0
    TI__Guru 51816 points

    Hi Kento,

    Communication is possible if the differential signal on the bus is created.

    I.e. with a fault on the CAN bus that shorts a CAN line to it's non-opposate state (CANH to Vcc / Vsup or CANL to ground), communication is possible for transmitting and receiving data because the differential signal on the bus can be created by the non-faulted signal line.  The level of signal degradation will be dependent on the system as the signal quality for complex systems can cause errors to occur in high speed systems. 

    For fault cases such as CANH short to ground, CANL short to Vcc / Vsup, or CANH short to CANL, communication typically fails due to not being able to drive the positive differential on the bus, thanks.

    Best Regards,

    Michael.

  • 0 in reply to Michael Ikwuyum
    TI__Expert 4555 points

    Hello Michael,

    Thank you for your response.

    Michael Ikwuyum said:
    with a fault on the CAN bus that shorts a CAN line to it's non-opposate state (CANH to Vcc / Vsup or CANL to ground), communication is possible for transmitting and receiving data because the differential signal on the bus can be created by the non-faulted signal line. 

    Let me share my opinion. If CANH is shorted to Vbat, CANH voltage goes to 12V. If CANL is normal, I believe CANL voltage moves between 2.5V (recessive bias voltage) and voltage lower than 2.5V (dominant voltage). In this case, CANH-CANL is always larger than VIT+, and thus always dominant. Therefore, two MCUs cannot communicate properly.

    Where do I misunderstand? Could you please correct my understanding?

    Thanks,

    Kento

  • 0 in reply to Kento Adachi
    TI__Guru 51816 points

    Hi Kento,

    Your understanding is correct if TXD is stuck low as the CAN bus follows the state of TXD.

    Presuming no concerns with TXD, the CAN bus may still be able to communicate as CANH can be toggling as high as Vbat and as low as GND with overall differential difference greater than 0.9 V as dominant and lower than 0.5 V as recessive. Hence, RXD data can be received correctly for proper MCU communication, thanks.

    Best Regards,

    Michael.