TCAN4550: Conduction Emission Failure

SATISH SOMANI

Part Number: TCAN4550

Hi team,

We have designed our product with two CAN ports located on the front panel. These ports are connected to each other during testing.

The CAN interface is implemented using the TCAN4550, which converts the MCU SPI interface to the CAN protocol. The schematic and layout were developed with reference to the TCAN4550EVM design.

During EMC compliance testing, we observed failures in the conducted emissions test (CISPR 32 Class A) when measurements were performed on the CAN port.

The CAN ports were interconnected using an unshielded CAT6A cable during the test. We would appreciate any guidance or recommendations regarding potential sources of emissions and possible mitigation techniques.

We have not mounted Common mode Choke (CMC) and Doesn't used any Y Cap.

1 month ago

0 SATISH SOMANI 1 month ago

Prodigy 10 points

I have added CE graph for the reference:

0 Jonathan Nerger 1 month ago in reply to SATISH SOMANI

TI__Mastermind 37811 points

Hello Satish,

Do you have the ability to add filter caps to GND on both the CANH and CANL pins? If so, please try to add some capacitance to the CAN signals to help filter and slow down the edge rates.

What does your termination look like? Is it a single 120 ohm resistor, or split termination with two 60 ohm resistors and a filter cap?

Do you have the ability to add a CMC to see if it makes any improvements?

Regards,

Jonathan

0 SATISH SOMANI 1 month ago in reply to Jonathan Nerger

Prodigy 10 points

Hi Jonathan,

Please help to review the schematic and layout of CAN section

0 Jonathan Nerger 1 month ago in reply to SATISH SOMANI

TI__Mastermind 37811 points

Hi Satish,

Yes, if you provide a schematic and layout file, I can review them.

Regards,

Jonathan

0 SATISH SOMANI 1 month ago in reply to Jonathan Nerger

Prodigy 10 points

Please find attached Sch pdf and LAyout filesTCAN4550_Schematic1.pdf

0 SATISH SOMANI 1 month ago in reply to SATISH SOMANI

Prodigy 10 points

Hi team,

Pls suggest Y cap values also?

0 Jonathan Nerger 1 month ago in reply to SATISH SOMANI

TI__Mastermind 37811 points

Hi Satish,

I am still reviewing the schematic and layout files. I see you already have 22nF caps on CANH and CANL. I don’t have a specific value to suggest and you may need to retest with different values to see if the results improve or get worse. Too much capacitance may lead to other communication errors if they filter the bus too much.

My first recommendation would be to install a CMC which is usually required in order to pass EMC tests.

Regards,

Jonathan

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TCAN4550: Conduction Emission Failure