ADM3054 1MHz Emission fails

From ADM3052 datasheets.

I see 1MHz is refresh frequency of pulse.

Is it same architecture?

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

Dear ConalW

Thank you for your comments.

I know what there is no detail about refresh pulse in ADM3054's datasheets.

But ...

- Connect 5V Vdd2 and check it LISN , we could see the figures as attached.

- With Near filed probe and Spectrum Analyzer , We Could see this noise near ADM3054.

Of course , the typical solution is add some capaciter to Vdd1 and vdd2.

But from some regulation of our products , we could not add capaciter in vdd2.

That's why , We have difficultly to reduce this noise.

Thanks & Best Regards,

And

ADM3053

http://www.analog.com/media/en/technical-documentation/data-sheets/ADM3053.pdf

DC CORRECTNESS AND MAGNETIC FIELDIMMUNITY

There is description of refresh pulse and periods.

So, we are thinking ADM3054 and ADM3053 using same architechture.

This question has been assumed as answered either offline via email or with a multi-part answer. This question has now been closed out. If you have an inquiry related to this topic please post a new question in the applicable product forum.

Thank you,
EZ Admin