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ADM3054 1MHz Emission fails

Dear Sir,

ADM3054 1MHz Emission fails

We are using ADM3054 for Can isolation transiver.


From Our EMC emission test , we can see every 1MHz noise (which over some limit line on 100MHz)

After some investigation , we have find ADM3054 make this noise.

- With Near field probe , ADM3054 make 1Mhz noise
- Check LISN and 5V line of ADM3054 VDD2, we find it as attaced.

I am not familiar with  the internal architecture of ADM3054.
Why AMD3054 make this noise?
From ADM3054 datasheets, It's seem there is no active switching components on ADM3054.

I hope your helps.

Best Regards,
 

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  • Hello medmshk,

    The ADM3054 does have details of the refresh on page 16 of the datasheet:

    In the absence of logic transitions at the input for more than ~1 μs, a periodic set of refresh pulses, indicative of the correct input state, are sent to ensure dc correct-ness at the output.

    Even so, we haven't seen this causing emissions issues. Are there any other possible sources of the 1 MHz on the same board? Even a simple switching regulator or something? Or are there any long unshielded and untwisted cables, for example, supplying 5V directly from a power supply on the bench? Even with such a set-up, I wouldn't expect such high emissions, but even for something else on the board, it's something that unfiltered/unshielded power cables could contribute.

    Finally, is there adequate decoupling of the Vdd1/Vdd2 on ADM3054, and appropriate capacitors on the board's power supplies.

    Best regards,

    Conal

Reply
  • Hello medmshk,

    The ADM3054 does have details of the refresh on page 16 of the datasheet:

    In the absence of logic transitions at the input for more than ~1 μs, a periodic set of refresh pulses, indicative of the correct input state, are sent to ensure dc correct-ness at the output.

    Even so, we haven't seen this causing emissions issues. Are there any other possible sources of the 1 MHz on the same board? Even a simple switching regulator or something? Or are there any long unshielded and untwisted cables, for example, supplying 5V directly from a power supply on the bench? Even with such a set-up, I wouldn't expect such high emissions, but even for something else on the board, it's something that unfiltered/unshielded power cables could contribute.

    Finally, is there adequate decoupling of the Vdd1/Vdd2 on ADM3054, and appropriate capacitors on the board's power supplies.

    Best regards,

    Conal

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