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ADUM2251 Side2 Slave don't respond


I have a design (see Appendix), that makes some communication problems.

I have double-checked logic low level thershold and it is more than 0,9V since

Vcc and Vcc-p is 5V.

I have read this thread

and  I have also watched the Video from MSCantrell "How I2C Isolators work"

Video which is super helpfull.

When I use the digital Isolator for some reasons the MAX1238, don't pull down the data-line when

it should transmit the data-pattern. With no digital isolator everything works fine.

Has anybody an idea or hint ?

Thanks for your support.

  • Hi Maximilian,

    There are a couple of questions I would like to ask before I can give a proper response.

    You have stated that the logic low level threshold is more than 0,9V this is occurring only on side 1 or side 2 of the ADuM2251? My initial guess is side 1 but I just wanted to make sure.


    The second question is do you have any scope screenshots of what you are seeing? A with and without isolator
    comparison would be nice. As well as a Side 1 and Side 2 snapshot as well.

    The last question is there some sort of communication going on at all? You mention that the MAX1238 doesn’t pull the data-line down but the details seem vague.


    Joseph Shim

  • 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.

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    EZ Admin