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Split termination Canbus?

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mImoto

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biased split termination

Hello,

I am usng the TJA1050 Can transceiver from Philips. It is recommended to use split termination with it. So, instead of a 120 Ohm resistor between CAN_L and CAN_H two series resistors of 60 Ohms with a 48nF capacitor from the point of connection between the two resistors to ground. My question is to which ground? the CAN_GND (ground of the transceiver)?. In an app.note says to a quiet ground but it doesn't say anything about connecting to the CAN_GND?. I would appreciate any help or information.

Thanks a lot and best regards,

mimoto
 

mr_ghz

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split termination biased

Hi mImoto,

A split termination is recommended to reduce emission. The best per-
formance is achieved by putting VDD/2 at the connection of the two
resistor. So you have a better common mode and better EMC.
This is called the 'biased split termination'. Another possibility is to
capacitively put this point to a reference. This reference is often GND,
but it could also be VDD.
So to answer your question: You can use CAN_GND, this would be a
good solution.

Bye
 

mImoto

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Thanks for the answer Mr_Ghz. Do you know by the way a doc where I can see an schematic of your biased split termination.

thanks again and best regards,

mimoto
 

mr_ghz

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Hi mImoto,

This document from Microchip describes the physical layer of CAN. It has
a (short) chapter over terminations.
<<http://www.microchip.com/download/appnote/analog/can/00228a.pdf>>

Bye
 

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