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TCAN1044A-Q1: Low-Cost Method to Enable/Disable CAN Bus Termination via Software in Automotive ECU

Shyamasundar Hegde
Prodigy 60 points
Part Number: TCAN1044A-Q1


Hello ,

am working on a two-wheeler automotive application using a CAN bus. Normally, CAN requires a 120 Ohm termination at each end of the bus. In my design, the ECU may sometimes be at the end of the bus and sometimes in the middle, so I want to enable or disable termination dynamically via software (using a GPIO or similar).

My requirements:

  • Automotive-grade solution (AEC-Q100/Q200 components)
  • Must handle ISO 11898 CAN fault conditions and ESD/load dump
  • Prefer split termination for EMC (two 60 Ohm capacitor)
  • Looking for a low-cost solution
  • Low power and compact (avoid mechanical relays if possible)

Questions:

  1. What is the best way to implement switchable termination in hardware for automotive CAN?
  2. Are there CAN transceivers with built-in termination control pins?
  3. If not, what analog switches or MOSFET-based solutions are recommended for automotive environments?

Any schematic examples or part recommendations would be helpful.

  • 0
    TI__Guru 57527 points

    Hi Shyamasunder,

    1. Using a MOSFET-based termination network (AEC-Q FETs) and placing the switching element where it survives bus faults

    • I.e., a switch termination network across CANH / CANL with the split termination (ensure midpoint is not left floating when off and can use a discharge path or a large 100 kohm bleed resistor to GND that remains connected when off) where the FET(s) connect / disconnect the network under the GPIO control. Basic gate protection can be added (series gate resistor + gate-source pull + clamp as needed). This can be enabled / disabled only when the bus is idle / at startup and not mid-frame as needed.

    2. Unfortunately, no.

    3. I would recommend reaching out to the FET team for their latest and greatest that can support VDS margins for your system (I.e., 12 V vs 24 V vs 48 V architectures, pulse transients, etc).

    I would also recommend to only have one ECU at each physical end of the bus have their termination enabled I.e., exactly only two terminations total on the bus similar figure 9-3 of the data sheet. See Controller Area Network (CAN) with Selectable Termination Reference Design for referenced examples, thanks.

    Best Regards,

    Michael.

  • 0 in reply to Michael Ikwuyum
    Prodigy 60 points

    Hi Michael , 

    If you have architecture or schematic for the point 1 ? Suppose if that is validated at TI we will consider it. 

    Regards,

    Shyam

  • 0 in reply to Shyamasundar Hegde
    TI__Guru 57527 points

    Hi Shyam,

    I would recommend reaching out / posting to the applicable SEM team if feasible and they may already have one similar to the referenced design.

    However, could you please help share your business case and timelines?

    I.e., what is the volume of CAN transceivers needed for the two wheeler automotive application and for what timeline? 

    Best Regards,

    Michael.