I have an application that uses many many ADuM5211s (about 74 per unit), and the product has been in production for some time. However, lately we are experiencing issues where the ADuM converter output goes to somewhere between 0.5V to 0.6V, and then just hangs there indefinitely. A check of the hung circuit showed a very level and smooth 0.5V output, no evidence of a misbehaving regulator, other than the voltage way off. The input was 5V, within 5%. The disable pin was firmly low.
We are using the ADuM as a 5V to 5V converter. Both the input and output sides have 10uF, 0.1uF and 0.01uF ceramic capacitors, to help reduce EMI (this product is required to be a part 15 class B device). The output voltage feedback is a 1K00 and 3K00 voltage divider.
When the circuits work (which is 90% of the time), the output is 5V and within the acceptable tolerance, and has less than 100mV of noise, which is also fine. When the circuit does not work, it just sits at a fraction of a volt. Strangely, touching or blowing or probing the circuit does not affect it, and it continues to hang. Blow a hot air tool at the ADuM, and it springs to life. (This is very repeatable, and repeatable on a great number of devices.) The output then regulates correctly at 5V and continues to do so, until powered off or disabled. Sometimes the device will work when re-enabled, and sometimes it doesn't.
Possibly related to this, are devices that are "slow to start", where the output does not switch on for several seconds, but they do eventually turn on and the output regulates at 5V indefinitely, once started.