TCAN1043-Q1: Termination Resistor

ABKD

Part Number: TCAN1043-Q1

Tool/software:

Hello,

I am using TCAN1043-Q1 CAN transceiver, if there are 10 nodes on CAN bus with 120-ohm termination resistor at each node, then the equivalent resistance between CAN H and CAN L will be only 12 ohms.

In this case, this is near to short circuit condition or if more nodes (100 as per datasheet) are connected max current will flow through the termination resistor?

So, the effective communication happens in this case ?

5 months ago

0 Sean Guo 5 months ago

TI__Mastermind 28150 points

Hi ABKD,

You are correct that if having 120 Ohms termination resistor on each node, the overall bus termination will be way less than the 60 Ohms termination required by CAN, that's why CAN usually recommend to put termination resistor only on both end nodes. You can also choose put a large value termination, i.e. 1.2K Ohms on non-terminating nodes, in that case the overall termination will still be around 60 Ohms, while having the benefit of termination resistor to reduce signal reflection.

Regards,

Sean

0 ABKD 5 months ago in reply to Sean Guo

Intellectual 300 points

Thanks for reply Sean Guo.

How this 120 ohm typical value arrived? What is the reason for 120 ohm, why not 100 ohm, 150 ohm or 270 ohm standard values?

Can you please let me know ?

+1 Sean Guo 5 months ago in reply to ABKD

TI__Mastermind 28150 points

Hi ABKD,

The purpose is to match the 120 Ohms path (cable) impedance. For more information on this topic, here is an app note:

https://www.ti.com/lit/an/slla270/slla270.pdf

Regards,

Sean

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TCAN1043-Q1: Termination Resistor