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About CAN Transceiver Bus Termination

Gary An
Intellectual 440 points

Hi all,

There are actually 2 method of bus termination which are the standard termination and split termination, I could find almost application is using split termination.

Which application standard application is used, and what is the advantage of standard application?

Thank you

  • 0
    TI__Guru 62920 points

    Hi Gary,

    My experiences are similar to yours in that it seems most applications prefer the use of split termination.  This makes sense, since with just an additional two components the termination network becomes an effective filter for higher-frequency common mode noise without degradation to the differential-mode signaling.  Still, some applications that are space- or cost-constrained and do not have very stringent EMC requirements may choose to opt for the "standard" termination shown above due to use of fewer components.

    Regards,
    Max

  • 0 in reply to Miguel Robertson
    Intellectual 440 points

    Thank you Max,

    Some device has STB pin to connect between the termination resistors on split termination, some device does not have STB pin.

    What is the different between connecting STB pin to the termination resistors and no STB pin?

    Can I design difference termination like split termination for the left side and standard termination on right side?

    Thank you

  • 0 in reply to Gary An
    TI__Guru 62920 points

    Hi Gary,

    Just to clarify, I am more used to seeing "STB" as the name for the pin that enables standby mode, and I think what you are referring to may be more commonly called "SPLIT" or "VREF."  This is a pin that provides a bias voltage of Vcc / 2 (the same bias level provided by each receiver in the recessive state).  This can be tied to a split termination network in order to more strongly bias the common mode voltage.  In some cases this can improve EMC performance.  Most newer devices are designed to meet common EMC performance targets without requiring this connection, though, so on most newer transceivers this pin is omitted.

    Even without a SPLIT pin, using a split termination network (two resistors and capacitor) is beneficial since the capacitance provides a low-impedance path to help shunt higher-frequency common-mode noise.  This improves RF emissions and noise immunity of the bus.

    It is OK to use a mix of "split" (two resistor + capacitor) and "standard" (one resistor) termination.

    Regards,
    Max