Many of the ADuM digital isolators, i.e. ADuM3300, have a 3V and 5V operating range for VDD1 and VDD2. The 3V range is 2.7 - 3.6V and the 5V range is 4.5 - 5.5V.
Is the device guaranteed to operate if the VDD supply is between 3.6 - 4.5V, albeit at 3V specs?
Yes, the device in your example will operate over the full 2.7 V to 5.5 V range. Performance is unspecified between the given ranges, but assuming that it meets the lower VDD parameters is a good conservative estimate.
Thank you very much.