TCAN334: Communication issue

sandeep kothapally

Part Number: TCAN334

Tool/software:

I made a board with TCAN334DCNR, and this board is interfacing with FPGA board through CAN protocol. TCAN334DCNR powered up with 3.3V and SN55HVD251DRJR (FPGA board) powered with 5V. Please look into the block diagram for more clarification. Does it work with this configuration?

5 months ago

0 Clemens Ladisch 5 months ago

Guru 316470 points

The CAN bus voltages are not directly related to the supply voltages, and in any case CAN receivers support a wide common-mode voltage range. This will work.

0 Ethan Sempsrott 5 months ago

TI__Genius 13302 points

Hi Sandeep,

I echo what Clemens said. 3.3V CAN transceivers are compatible with 5V transceivers since CAN is a differential protocol. The document below is a great resource for understanding why these are compatible:

https://www.ti.com/lit/an/slla337/slla337.pdf

Let us know if that answers your question!

-Ethan

0 sandeep kothapally 4 months ago

Prodigy 100 points

Thanks for your support. Sorry for delay. Can you check the schematic once?

TVS diode and R96, R97 not populated.

0 Ethan Sempsrott 4 months ago in reply to sandeep kothapally

TI__Genius 13302 points

Hi Sandeep,

I am out of office on business travel until 4/23 but I aim to respond to your question by middle of next week.

Best,

Ethan

0 Ethan Sempsrott 4 months ago in reply to Ethan Sempsrott

TI__Genius 13302 points

Hi Sandeep,

My only comment for that schematic is that the termination resistors and split termination capacitor are not valued properly.

First, only the 2 end nodes in a CAN bus should have 120 Ohm termination (120 Ohm in total for one node). So R98 and R99 should be 60 Ohms, which in series is 120 Ohms.

Second, the typical split termination capacitor recommended to be 4.7nF.

For some more information on split termination, this document has a section on it: https://www.ti.com/lit/an/sloa101b/sloa101b.pdf

Let me know if that helps or if you have any further questions,

-Ethan

0 sandeep kothapally 4 months ago in reply to Ethan Sempsrott

Prodigy 100 points

Hi Ethan,

Thaks for your review. I have given 120 Ohm termination on the board. R98 is 120 ohm and R99 is 0R. Is capacitor necessary??

0 Ethan Sempsrott 4 months ago in reply to sandeep kothapally

TI__Genius 13302 points

Hi Sandeep,

What you are describing is called standard termination. This is where a single 120 Ohm resistor is tied to CANH and CANL. In this configuration, R99 and C41 should be removed. This capacitor helps to filter out unwanted frequencies in particular systems that need them.

This other E2E post goes into some more detail about the differences between standard and split termination configurations:

https://e2e.ti.com/support/interface-group/interface/f/interface-forum/900648/about-can-transceiver-bus-termination

Again, that previous link I sent also explains the split termination configuration and why the capacitors is used.

Best,

Ethan

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TCAN334: Communication issue