topic Re: Recommended Filtering/Termination for CAN (LPC11C24) in LPCXpresso IDE

Recommended Filtering/Termination for CAN (LPC11C24)

lpcware — Thu, 16 Jun 2016 00:28:07 GMT

Content originally posted in LPCWare by Caradhras on Thu May 31 14:22:18 MST 2012
Hi,

the LPCXpresso-Board shows a simple split-termination and nothing else for the CAN-Transceiver.

I fear, it will not be very resistant to bad things in terms of EMC. Is there anything that can be recommended? I saw circuits that have chokes around CAN-L and -H, for example here (german document):

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CDEQFjAA&url=http%3A%2F%2Fwww.fh-zwickau.de%2Ffileadmin%2Fugroups%2Fftz%2FPublikationen%2FProf_Sperling%2F1999_EMV.pdf&ei=UtzHT_uWOs_FtAai9-mqDg&usg=AFQjCNEeWv29DblOIpqnneTt4t8MayoYEw

Is there any "standard-circuit" or best practice? I didnt find an application note concerning this. :( The LPC11C24 will be placed in a very dirty environment (near an inverter).

Help would be greatly appreciated. :)

Re: Recommended Filtering/Termination for CAN (LPC11C24)

lpcware — Thu, 16 Jun 2016 00:28:08 GMT

Content originally posted in LPCWare by Ex-Zero on Thu May 31 15:24:43 MST 2012

Quote: Caradhras
I didnt find an application note concerning this.

:confused:

Google "CAN BUS choke" :)

http://www.ti.com/lit/an/slla271/slla271.pdf

or

http://www.google.de/url?sa=t&rct=j&q=can%20bus%20choke&source=web&cd=3&sqi=2&ved=0CG8QFjAC&url=http%3A%2F%2Fwww.lairdtech.com%2FWorkArea%2Flinkit.aspx%3FLinkIdentifier%3Did%26ItemID%3D3164&ei=8ezHT9uKM4qMswbFyoHVDg&usg=AFQjCNE0FgB_aihevPRKaO50X7_0oVYB9w&cad=rja

Re: Recommended Filtering/Termination for CAN (LPC11C24)

lpcware — Thu, 16 Jun 2016 00:28:08 GMT

Content originally posted in LPCWare by Ex-Zero on Thu May 31 15:25:28 MST 2012

Quote: Caradhras
I didnt find an application note concerning this.

Re: Recommended Filtering/Termination for CAN (LPC11C24)

lpcware — Thu, 16 Jun 2016 00:28:09 GMT

Content originally posted in LPCWare by NXP_Europe on Thu May 31 15:37:32 MST 2012
Hello Caradhras,

The CAN transceiver used inside the lpc11C24 looks like the TJA1050.

http://www.nxp.com/documents/application_note/AN00020.pdf

You have to take special pcb-design precautions. Use different layers and gnd shields. On our NXP-site some app-notes deal about EMC.

Use the lowest speed you need.

From personal experience using CAN, I know that it works good. Giving little problems, even at long distances (500 m 125 kB).

Re: Recommended Filtering/Termination for CAN (LPC11C24)

lpcware — Thu, 16 Jun 2016 00:28:10 GMT

Content originally posted in LPCWare by martinho on Thu May 31 23:06:06 MST 2012
I'm using CAN-Bus networks for more then 10 years, and can tell You that we do not use any choke, we never had problem passing the restrictive automotive EMC regulations. If You have a very noisy environment (inverter?) it is good practice to isolate the CAN-Bus ground from the Power ground (isolated DC/DC converter?). Be award, the CAN-Bus is differential but needs a good ground.

Re: Recommended Filtering/Termination for CAN (LPC11C24)

lpcware — Thu, 16 Jun 2016 00:28:10 GMT

Content originally posted in LPCWare by Ex-Zero on Fri Jun 01 00:43:56 MST 2012
Higher baudrates and harsh environment can cause problems, as many (also non german) articles describe :mad:

If you want to avoid this, adding a choke in your layout is improving your data reliabilty :D

If you're not sure if you need them or not, a simple data transmission test with 1 Mbit (a few days) can help you to decide :)

Ordering code for Epcos B82789 chokes and board layout is shown here:

http://www.epcos.com/web/generator/Web/Sections/Components/Page,locale=en,r=263282,a=601062.html?_requestid=223464

and available here:

http://uk.farnell.com/epcos/b82789c0104n001/choke-canbus-1812-100uh-0-15a/dp/1644874

Re: Recommended Filtering/Termination for CAN (LPC11C24)

lpcware — Thu, 16 Jun 2016 00:28:11 GMT

Content originally posted in LPCWare by Caradhras on Fri Jun 01 02:21:00 MST 2012
Thank you very much! You already helped me out!