ADuM3160 Communication Problem

I am working on a board that was recently revised to include an ADuM3160.  It is quite similar to circuit posted by Jie in "ADuM3160 configuration" on 2/2/12.  Note: The DD+ pullup is in our circuit.

5 out of 10 boards get discovered by the host PC and communications work (mostly).  However, the other 5 enumerate and do not communicate at all.  Our software is mature and seemingly has been stable. 

We have played around and popped parts on and off, retouched solder joints, run SnoopyPro, etc.  When we take the part completely off and jumper the USB signals straight through, board and software works OK.

Any comments and/or suggestions welcomed. 

  • 0
    •  Analog Employees 
    on Feb 10, 2012 3:36 AM

    Hello JohnG,

    Intermittent behavior in digital systems is usally due to contention.  I would start with the pullup on the DD+  line.  Make sure that if you added a pullup, that there is not an internal pullup in your micro as well.  The next thing to do is check the power supply connections and be sure that you have a valid arrangement of voltages.  Then review that the SPU, SPD, PIN, and PDEN pins are pulled to 3.3V.  Past that I think I would need to see a schematic.

    If you could check the voltages on the pins when it is not communicating it would also be helpful.

    Best Regards,

    MSCantrell

  • I checked into it and came up with the following;

    • There is a 1.5K pullup on PIN to +3.3V. 
    • The LPC2468 pullup/down resistors are disabled.

    Voltages are;

  • 0
    •  Analog Employees 
    on Feb 15, 2012 12:14 AM

    Hi JohnG,

    Assuming that VBUS in your application is Vbus2, that should be supplied with 3.3V if it is tied to VDD2 or it should be 5V if it is not tied to VDD2 and the internal regulator is active.  2.3V on the power pins of the downsream side is probably below the under voltage lockout threshold.  Please check the side 2 power connections.

    MSCantrell

  • 0
    •  Analog Employees 
    on Aug 2, 2018 4:33 PM
    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