TCAN1473-Q1: Question about EMC test fail

Dear Michael,

Thank you for your support.

I understand that TCAN1473-Q1 has no problem about EMC test if I follow your suggestions below. -> Am I right?

I will check your suggestions with my customer.

Still I am confused, Why TCAN1473-Q1 have a problem although TCAN1472-Q1 do not have? Is the structure inside different?

Best regards,

Chase

Hi Chase,

These are some of the major suggestions. However, EMC can be very sensitive to the system environment and customers would have to debug case by case as needed.

I.e., Their existing reports available on seismic show that they both pass and you may compare the test reports to further help narrow down what may be different per their passing (1473) / failing (1472) observations within the system / layout / PCB as well, thanks.

Best Regards,

Michael.

Dear Michael,

Here are the feedbacks from my customer ;

• Ensure the power supplies do not droop. For example, confirm VCC is at 5 V when measured at the IC pin, and not somewhere near 4.75 V.
  -> Power supply is stable. measured as 5V at anywhere.
• Ensure total bus load or any other nodes connected ≤ 50 pF. -> TVS(7pF)+CAP(7pF) = TOTAL 14pF
• Ensure the previous passing case did not include CMC, similar to the NC CMC as this case. Verify if it passes with CMC. Ensure CMC of 50 to 100 uH passes. -> TCAN1462 : Passed without CMC. TCAN1473 : Passed only if CMC is added. Below screenshot is the image of passed results of TCAN1462.
• 
• 
• Ensure the previous case includes a similar termination as this case (or help confirm any / all differences in from the passing case). Verify if it passes with 60 ohms split termination at both ends of the bus for an effective bus termination of 60 ohms. -> TCAN1462 is recommended as 60ohm, and TCAN1473 is recommended as 2.2Kohm in EVM. So it is different.
• Ensure cable impedance is close to 120 ohms as well -> It is very close to 120ohm.

Best Regards,

Chase

Dear Michael,

Here are more things ;

I am not a member of TI, so I cannot see seismic link. Could you share it using different ways?

And my mistake in previous post, passed device is TCAN1462, not TCAN1472.

And last, Do you think that the schematic of TCAN1473-Q1 in my first post have no problem? Could you check if I send layout to you?

Best regards,

Chase

Hi Chase,

Thanks for clarifying. Please help contact your regional TI representative to help provide the contents from the link as needed.

However, could you help verify the device passes with a similar termination from the passing case? Thanks.

Best Regards,

Michael. 

Dear Michael,

Thank you for your support.

- Could you help verify the device passes with a similar termination from the passing case?

=> You mean that It is necessary to test with 60 ohm resistor instead of 2.2kohm although EVM's recommendation is 2.2kohm?

Best regards,

Chase

Hi Chase,

Yes, I am recommending an effective bus impedance of 60 ohms. See below example from the EVM, thanks.

Best Regards,

Michael.

Dear Michael,

Thank you for your support.

Customer said that it is not easy to test with 60 ohm because it is dedicated value in test process.

Is there any internal difference between TCAN1473-Q1 and TCAN1462-Q1? (exclude termination resistor)

Hi Chase,

No known major difference internally as I suspect concerns are externally related.

I.e, noise may be expected with impedance mismatches and may further confirm with the passing device + the mismatched impedance case as well, thanks.

Best Regards,

Michael.