SLOA101B August 2002 – May 2016 SN55HVD233-SEP , SN65HVDA1040A-Q1 , SN65HVDA1050A-Q1 , SN65HVDA540-5-Q1 , SN65HVDA540-Q1 , SN65HVDA541-5-Q1 , SN65HVDA541-Q1 , SN65HVDA542-5-Q1 , SN65HVDA542-Q1
Reference voltage on a CAN transceiver is the Vref pin (pin 5) of what is considered to be the standard CAN transceiver footprint. This is the footprint of the first CAN transceiver to market, the NXP PCA82C250.
When first introduced, the Vcc/2 Vref pin served a particular NXP CAN controller as a voltage reference used to compare the bus voltage of a remaining single bus line in the event of an accident. If the voltages were the same, it was a recessive bit; if different, it was a dominant bit.
Although some users consider it handy for use as an actual voltage reference at the node, it is typically unused.