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CAN termination resistor purpose?
Termination resistor prevents signal rebound, like waves hitting a wall. If the value of the resistor does not match the characteristic impedance of the cable, reflection may occur. In most RS485 configurations, two termination resistors are used. One of each is placed at the extreme end of the twisted pair cable.
CAN Bus termination 120 Ohm?
It is well known, in the CAN community at least, that every CAN and CAN FD network should be terminated with a 120 Ohm resistor at each end of the bus. If your termination is correct, you should read approximately 60 Ohms (two 120 Ohm resistors in parallel produce a resistance of 60 Ohms).
CAN resistance tolerance be terminated?
A CAN Bus network must have a terminating resistor between CAN High and CAN Low for it to work correctly. The resistance should ideally be less than 120 Ohms and closer to 60 Ohms if a resistor is fitted at each end of the bus.
Why can you only use 120 ohm?
Terminal resistors are needed in CAN bus systems because CAN communication flows are two-way. The termination at each end absorbs the CAN signal energy, ensuring that this is not reflected from the cable ends. Hence 120 Ohm termination adaptors are considered the standard for CAN bus.
Where does the termination resistor go?
4 Answers. Termination resistors sit at one of two places: As close to the driver as possible (for source termination), or as close to the end of the trace as possible (for the kind of termination that you have).
Can you use one 60 ohm resistor instead of two 120 ohm?
If you don’t have two 120-ohm resistors, you can accomplish the termination (on a small network) with a single 60 ohm resistor (120 in parallel with 120 is 60) or anything close 55-65 is fine. I found a document saying this workaround is a mistake, but it does not provide why.
Can a 60 Ohm termination be used in a lab?
It seems that many engineers use such a workaround. a single 60 ohm termination for lab testing when bus is only a few feet (probably not allowed, but it works).
What kind of resistor should be used for can termination?
It is well known, in the CAN community at least, that every CAN and CAN FD network should be terminated with a 120 Ohm resistor at each end of the bus.
Why do we use only 120 ohms resistance at terminals?
That is well approximated by f,max = 1/ (2*Tr) where Tr is the rise time (defined 30%-60% of the final voltage level, conservatively). Why it’s 120 is simply a function of the design limited by physical size. It isn’t specifically important which value they picked within a broad range (for example, they could have gone with 300 Ohms).