ADuM5401 and Tri-State Input

I am using the CN-0336-EVAL board which has an AD7091R adc and a ADuM5401.  I'm having trouble with the MISO/SDATA being pulled low when the device is not selected.  It should go to high impedance after clocking the data out.  I was wondering, since the SDATA line goes to Vid on the ADuM5401 which outputs on Vod to my microcontroller, what does the ADuM5401 do with a high impedance input.  Does it output low on the Vod pin when the Vid pin is high impedance?  I have more than one device hooked to the SPI bus and it would be nice if the MISO/SDATA would get released.

Thanks for your help.

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    •  Analog Employees 
    on Sep 7, 2017 12:00 AM

    nirb81: What you suggested looks like it would work.  Instead of the ADuM5401, If you use the ADuM5411, which has the same function as the ADuM5401, but with only 30mA output (not 100mA output of the ADuM5401),  the ADuM5411 has a pin called VE1 which will disable the VOD pin, and you won't need to add the SN74AHC1G125.  The ADuM5411 is in a smaller package with less creepage than the ADum5401, so you may want to review the datasheet for your application needs.

    Regards, Brian

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  • 0
    •  Analog Employees 
    on Sep 7, 2017 12:00 AM

    nirb81: What you suggested looks like it would work.  Instead of the ADuM5401, If you use the ADuM5411, which has the same function as the ADuM5401, but with only 30mA output (not 100mA output of the ADuM5401),  the ADuM5411 has a pin called VE1 which will disable the VOD pin, and you won't need to add the SN74AHC1G125.  The ADuM5411 is in a smaller package with less creepage than the ADum5401, so you may want to review the datasheet for your application needs.

    Regards, Brian

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